Circadian-friendly led light sources

ABSTRACT

Methods and apparatus for providing circadian-friendly LED light sources are disclosed. A light source is formed to include a first LED emission (e.g., one or more LEDs emitting a first spectrum) and a second LED emission (e.g., one or more LEDs emitting a second spectrum) wherein the first and second LED emissions are combined in a first ratio and in a second ratio such that while changing from the first ratio to the second ratio the relative circadian stimulation is varied while maintaining a color rendering index above 80.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/996,143filed on Jan. 14, 2016, which is a continuation-in-part of U.S.application Ser. No. 14/316,685 filed on Jun. 26, 2014, entitled,“CIRCADIAN FRIENDLY LED LIGHT SOURCE”, which is entitled to priorityunder 35 U.S.C. § 119(e) of U.S. Provisional Application No. 61/871,525filed on Aug. 29, 2013; also 14/996,143 filed on Jan. 14, 2016 is acontinuation-in-part of U.S. application Ser. No. 14/819,010 filed onAug. 5, 2015, entitled, “FILTERS FOR CIRCADIAN LIGHTING”, which isentitled to priority under 35 U.S.C. § 119(e) of U.S. ProvisionalApplication No. 62/033,487 filed on Aug. 5, 2014, entitled, “FILTERS FORCIRCADIAN LIGHTING”, and Ser. No. 14/996,143 filed on Jan. 14, 2016claims benefit under 35 U.S.C. § 119(e) to U.S. Provisional ApplicationNo. 62/103,472 filed on Jan. 14, 2015, entitled, “CIRCADIAN-FRIENDLY LEDLIGHT SOURCES”, each of which are incorporated by reference in theirentireties.

FIELD

The disclosure relates to the field of illumination products and moreparticularly to apparatus and methods for providing circadian-friendlyLED light sources.

BACKGROUND

Identification of non-visual photoreceptors in the human eye (so-calledintrinsically photosensitive retinal ganglion cells, or “ipRGCs”) linkedto the circadian system has sparked considerable interest in the effectsof various light spectra on health and amenity for human beings. Highcircadian stimulation may lead to positive effects such as resettingsleep patterns, boosting mood, increasing alertness and cognitiveperformance, and alleviating seasonal affective depression. However,mis-timed circadian stimulation can also be associated with disruptionof the internal biological clock and melatonin suppression, and may belinked to illnesses such as cancer, heart disease, obesity and diabetes.

Circadian stimulation is associated with glucocorticoid elevation andmelatonin suppression and is most sensitive to light in the bluewavelength regime. With the preponderance of light-emitting diode (LED)illumination products being based on blue-primary phosphor-convertedwhite-emitting LEDs, the situation has developed that most LED-basedillumination sources have higher levels of circadian stimulation thanthe traditional sources they are intended to replace.

Legacy techniques have been studied and in some cases techniques fordealing with circadian stimulation in lighting products have beenpublished (e.g., see WO 2014165692 to Moore-Ede et al.), however suchlegacy techniques are deficient, at least in regards to uses of theherein-disclosed techniques to address lighting system design withrespect to diurnal or circadian cycles

In addition, illumination products are rarely tunable (other than meredimming), and legacy illumination products fail to address the impact onhumans with respect to diurnal or circadian cycles. Still worse, legacyillumination products that are ostensibly tunable fail to produce goodcolor rendering throughout the tunable range.

What is needed is a technique or techniques for constructingillumination products in which light emission (e.g., LED light emission)can be controlled to provide varying levels of circadian stimulationwhile providing desirable light quality aspects such as correlated colortemperature (CCT) and color rendering index (CRI). Also needed is anillumination system in which a first ratio and a second ratio of lightemission are such that changing from the first ratio to the second ratiovaries relative circadian stimulation while maintaining a CRI above 80and maintaining the CCT within a prescribed range.

The aforementioned legacy technologies do not have the capabilities toimplement a circadian-friendly LED light sources in an efficient manner.Therefore, there is a need for improved approaches.

SUMMARY

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its purpose is to present someconcepts of the invention in a simplified form as a prelude to the moredetailed description that is presented later.

Regarding human circadian system stimulation, positive benefits can berealized and the deleterious ones avoided by stimulating a circadianlight cycle in a way similar to that which occurs in nature (sunlightaction over the course of the day), i.e., bright illumination levelsassociated with high blue content in the morning and midday, and lowerlight levels and greatly reduced blue content in the evenings.

The embodiments disclosed herein describe how to make and use variouscombinations of different LED emission spectra, and how to make whitelight sources that can be tuned to cycle through ranges fromhigh-circadian-stimulating light to less-circadian-stimulating lightwhile maintaining reasonable color rendering (CRI>80 and R9>0) and whitecolor point.

The various embodiments (e.g., lamps and displays) are tuned to emitlight in cycles (e.g., diurnal cycles) that range fromhigh-circadian-stimulating light to less-circadian-stimulating light.

In a first aspect, light sources are provided comprising at least onefirst LED emission source characterized by a first emission, and atleast one second LED emission source characterized by a second emission;wherein the first emission and the second emission are configured toprovide a first combined emission and a second combined emission, thefirst combined emission is characterized by a first SPD and fractionsFv1 and Fc1; the second combined emission is characterized by a secondSPD and fractions Fv2 and Fc2; Fv1 represents the fraction of power ofthe first SPD in the wavelength range from 400 nm to 440 nm; Fc1represents the fraction of power of the first SPD in the wavelengthrange from 440 nm to 500 nm; Fv2 represents the fraction of power of thesecond SPD in the wavelength range from 400 nm to 440 nm; Fc2 representsthe fraction of power of the second SPD in the wavelength range from 440nm to 500 nm; the first SPD and the second SPD have a color renderingindex above 80; Fv1 is at least 0.05; Fc2 is at least 0.1; and Fc1 isless than Fc2 by at least 0.02.

In a second aspect, light sources are provided comprising an LED deviceconfigured to emit a primary emission; one or more wavelength conversionmaterials optically coupled to the primary emission; wherein a portionof the primary emission is absorbed by the wavelength conversionmaterials to produce a secondary emission; wherein a combination of theprimary emission and the secondary emission produces white lightcharacterized by an SPD having a CCT and a color rendering index;wherein at least 5% of the SPD power is in a wavelength range from 400nm to 435 nm; wherein a circadian stimulation of the SPD is less than80% of a circadian stimulation of a reference illuminant having the samecolor temperature; and wherein the white light is characterized by acolor rendering index above 80.

In a third aspect, lighting systems are provided comprising an LEDdevice configured to emit a primary emission characterized by a primarySPD; at least one phosphor optically coupled to the primary emission,wherein the at least one phosphor is characterized by saturableabsorption within a blue-cyan wavelength region; wherein the LED deviceis configured to be controlled by a power signal configured to dim theprimary emission; wherein at a first power level the system emits afirst SPD characterized by a first fraction fc1 of spectral power in awavelength range from 440 nm to 500 nm and a first CCT; wherein at asecond power level the system emits a second SPD characterized by asecond fraction fc2 of spectral power in a wavelength range from 440 nmto 500 nm and a second CCT; and wherein the second power level is lessthan the first power level and the second fraction fc2 is less than 80%of the first fraction fc1.

In a fourth aspect, light emissions having specific Circadian-friendlyemission peaks are made using blends of selected wavelength-convertingmaterials.

In a fifth aspect, a method is provided of using a lighting system toemit emitted light having a relatively high illuminance but a relativelylow circadian stimulation, said light system having at least onesolid-state lighting emitter, and at least a first and second additionallight emitters for cooperating with said lighting emitter such that saidemitted light is white light. The method comprises applying power tosaid lighting system thereby causing at least said light emitter andsaid first and second additional light emitters to emit said emittedlight having a certain correlated color temperature (CCT), the lightingsystem being configured to produce an illuminance of about 50 lux toabout 5000 lux, and a circadian stimulation no greater than about 50% ofa reference circadian stimulation of a reference illuminant configuredto produce an illuminance essentially the same as said predeterminedilluminance and a CCT the same as said certain CCT.

In various embodiments of the above aspects or any other aspect of theinvention delineated herein, circadian stimulation is no greater thanabout 20% of said reference circadian stimulation. In one embodiment,the light emitter comprises at least one light-emitting diode or onelaser diode emitting having a peak wavelength in a range 400-430 nm, thefirst additional light emitter has an emission spectrum having a peakbetween 500 nm and 550 nm, and the second additional light emitter hasan emission spectrum having a peak between 600 nm and 670 nm. In anotherembodiment, the emitted light is characterized by a spectral powerdistribution (SPD), wherein the SPD has a local minimum in a spectralregion between 440 nm and 480 nm and a power in the SPD between 440 nmand 480 nm is less than 2% of a power of the SPD between 380 nm and 780nm. In yet another embodiment, the emitted light has a CRI Ra higherthan 80 and a CRI R9 higher than 0. In still another embodiment, theemitted light has a CRI R9 higher than 80. In another embodiment, thecertain CCT is at least 2700K and a distance from the Planckian locusDuv which is smaller than +/−0.006. In yet another embodiment, theilluminance is a retinal illuminance. In still another embodiment, thefirst and second additional light emitters are phosphor light-convertingmaterials. In another embodiment, the reference illuminant is a CIE CRIreference illuminant. In another embodiment, the method furthercomprises selecting a circadian action spectrum, and wherein saidcircadian stimulation is calculated as an integral of said SPD weighedby said circadian action spectrum. In yet another embodiment, thelighting system comprises no light emitting species having a peakemission at a wavelength in a range 440-490 nm.

In various embodiments of the above aspects or any other aspect of theinvention delineated herein, the area under the SPD within a range of440 nm and 480 nm is less than 0.5% of the area under the SPD within arange of 380 nm to 780 nm. In one embodiment, the SPD is characterizedby a correlated color temperature (CCT) which is greater than or equalto 2700K. In another embodiment, an absolute distance from the Planckianlocus (Duv) is less than 0.006. In yet another embodiment, the systemcomprises a general CRI index (Ra) is greater than or equal to 80. Instill another embodiment, the system comprises a special CRI index #9(R9) is greater than or equal to 0. In yet another embodiment, the firstphosphor and the second phosphor are disposed in layers or in a patternof small patches around the LED pump. In another embodiment, the systemfurther comprises a filter substantially absorbing or reflecting lighthaving a wavelength within a range of 430 nm to 490 nm. In oneembodiment, the filter does not significantly affect a chromaticity ofthe emitted light.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art will understand that the drawings, describedherein, are for illustration purposes only. The drawings are notintended to limit the scope of the present disclosure.

FIG. 1A is a diagram showing a circadian stimulation wavelength range asused to tune a circadian-friendly LED light source, according to someembodiments.

FIG. 1B shows how the impact of a light source on the circadian systemscales against light intensity.

FIG. 1C shows a relative circadian stimulation for 3300K white lightsources composed of a primary LED (varying from violet- toblue-emitting) combined with a green-emitting and red-emitting phosphorfor different full-width half-maxima of circadian stimulation wavelengthranges peaked at 465 nm, according to some embodiments.

FIG. 1D shows SPDs for 3300K white light sources composed of a primaryLED (varying from violet- to blue-emitting) combined with agreen-emitting and red-emitting phosphor, normalized to emission at 600nm according to some embodiments.

FIG. 1E shows the circadian stimulation for a two-phosphor based LEDwhite light source at 3300K as a function of the primary LED emissionpeak wavelength, according to some embodiments.

FIG. 1F shows predicted melatonin suppression versus illuminance at theeye level, for a 90 min exposure, according to some embodiments.

FIG. 2A shows spectral power distributions (SPDs) of various wavelengthcombinations as used in configuring a circadian-friendly LED lightsource, according to some embodiments.

FIG. 2B shows an SPD corresponding to a first LED emission as used inconfiguring a circadian-friendly LED light source, according to someembodiments.

FIG. 2C shows an SPD corresponding to a second LED emission as used inconfiguring a circadian-friendly LED light source, according to someembodiments.

FIG. 3A is a chart showing color rendering properties exhibited by acircadian-friendly LED light source at three different colortemperatures, according to some embodiments.

FIG. 3B is a chart showing relative circadian stimulation resulting froma circadian-friendly LED light source at three different colortemperatures, according to some embodiments.

FIG. 4A shows an example of a light strip used to implement a whitelight source that is tunable based on measurable aspects and/or changesin the environment, according to some embodiments.

FIG. 4B shows a narrower band (Gaussian) circadian stimulation rangewith 30 nm full-width-half-maximum (FWHM) and peaked at 465 nm.

FIG. 4C shows emission of a first violet-pumped two-phosphor LED (right)and a second violet-pumped blue-phosphor LED (left), according to someembodiments.

FIG. 4D shows the individual and combined LED-based emission spectra ofFIG. 4C.

FIG. 4E shows emission of a (right) first violet-pumped two-phosphor LEDand a (left) second blue-emitting LED, according to some embodiments.

FIG. 4F shows the individual and combined LED-based emission spectra ofFIG. 4D.

FIG. 4G shows circadian stimulation as a function of color temperaturefor certain light sources.

FIG. 4H shows a light strip having two different sets of LED-basedemitters and a clock/timer, control circuits, and a driver to controlthe ratio of emissions of the two different sets of LED-based emittersto implement a circadian-friendly LED white light source, according tosome embodiments.

FIG. 4I shows measured SPDs for two display systems with a white screen,according to some embodiments.

FIG. 4J shows predicted melatonin suppression, according to someembodiments.

FIG. 4K shows an example of a spectrum emitted by a white screen,according to some embodiments.

FIG. 4L illustrates relevant spectra for a typical LED-lit liquidcrystal display, according to some embodiments.

FIG. 4M shows calculated relative circadian stimulation and relativedisplay efficacy.

FIG. 4N shows embodiments for which the phosphor system is tuned tobetter work with a chosen primary peak emission wavelength, according tosome embodiments.

FIG. 5A is a chart showing a linear chromaticity curve in x-ychromaticity space as produced by a circadian-friendly LED light source,according to some embodiments.

FIG. 5B is a chart showing the shape of a white light bounding region asproduced by a circadian-friendly LED light source, according to someembodiments.

FIG. 5C shows characteristics of two sets of LED-based sources that arecontrolled independently, according to some embodiments.

FIG. 6 shows an exploded view of an assembly view of an LED lamp forminga circadian-friendly LED light source, according to some embodiments.

FIG. 7 shows a schematic of a multi-track driver control system as usedin an LED lamp employing a circadian-friendly LED light source,according to some embodiments.

FIG. 8 shows two strings of LEDs in an intermixed physical arrangementto form a two-channel, circadian-friendly arrangement as used in an LEDlamp, according to some embodiments.

FIG. 9A presents a selection of lamp shapes corresponding to variousstandards, according to some embodiments.

FIG. 9B presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9C presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9D presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9E presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9F presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9G presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9H presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 9I presents one selection of troffers corresponding to variousshapes, according to some embodiments.

FIG. 10A depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10B depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10C depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10D depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10E depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10F depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10G depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10H depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 10I depicts one embodiment of the present disclosure in the form oflamp applications, according to some embodiments.

FIG. 11A shows an initial SPD of a white LED source, and a filtered SPDafter blue light is blocked by a filter, according to some embodiments.

FIG. 11B shows an initial SPD of a white LED source and the convertedSPD after blue light is absorbed by a “circadian phosphor” and convertedto yellow light, according to some embodiments.

FIG. 12 shows an emission spectrum of a white LED light source with aCCT of 3000K and a CRI of about 90, and the emission and absorptionspectra of a saturable red phosphor, according to some embodiments.

FIG. 13 shows a possible way to combine such a white LED light sourcewith such a saturable phosphor, according to some embodiments.

FIG. 14A shows the resulting spectral properties of the system shown inFIG. 13, according to some embodiments.

FIG. 14B shows the resulting colorimetric properties of the system shownin FIG. 13, according to some embodiments.

FIG. 15A depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15B depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15C depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15D depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15E depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15F depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15G depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15H depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 15I depicts one embodiment of the present disclosure as can beapplied toward lighting applications.

FIG. 16A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 16B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 16C shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 16D shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 17A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 17B shows example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 18A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 18B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 18C shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 18D shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 18E shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 19A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 19B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 19C shows examples using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 20A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 20B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 20C shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 21A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 21B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 22 shows examples using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 23 shows examples using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 24A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 24B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 25A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 25B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 25C shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 25D shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 25E shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 26A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 26B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 26C shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 27A shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 27B shows an example using dielectric stacks and compares filteredSPDs under varying conditions, according to some embodiments.

FIG. 28A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 28B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 29A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 29B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 30A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 30B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 31A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 31B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 32A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 32B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 33A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 33B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 34A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 34B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 35A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 35B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 36A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 36B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 37A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 37B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 38A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 38B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 39A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 39B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 40A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 40B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 41A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 41B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 42A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 42B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 43A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 43B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 44A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 44B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 45A compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 45B compares experimental results to conventional LED spectra,according to some embodiments.

FIG. 46 depicts a CCT curve as it varies over input power, according tosome embodiments.

FIG. 47 depicts a CCT curve as it varies over input power, according tosome embodiments.

FIG. 48A depicts various 3-way bulbs in an A-lamp form factor, accordingto some embodiments.

FIG. 48B depicts various 3-way bulbs in an A-lamp form factor, accordingto some embodiments.

FIG. 48C depicts various 3-way bulbs in an A-lamp form factor, accordingto some embodiments.

FIG. 48D depicts various 3-way bulbs in an A-lamp form factor, accordingto some embodiments.

FIG. 48E depicts various 3-way bulbs in an A-lamp form factor, accordingto some embodiments.

FIG. 49A depicts emission peaks using blends of selectedwavelength-converting materials, according to some embodiments.

FIG. 49B depicts emission peaks using blends of selectedwavelength-converting materials, according to some embodiments.

FIG. 49C depicts emission peaks using blends of selectedwavelength-converting materials, according to some embodiments.

FIG. 50A illustrates characteristics of displays and components thereto,in accordance with some embodiments.

FIG. 50B illustrates characteristics of displays and components thereto,in accordance with some embodiments.

FIG. 50C illustrates characteristics of displays and components thereto,in accordance with some embodiments.

FIG. 50D illustrates characteristics of displays and components thereto,in accordance with some embodiments.

FIG. 51A illustrates reduced loss by providing a spectrum that alreadyhas only a small portion of radiation in the CSR.

FIG. 51B illustrates reduced loss by providing a spectrum that alreadyhas only a small portion of radiation in the CSR.

DETAILED DESCRIPTION

Reference is now made in detail to certain embodiments. The disclosedembodiments are not intended to be limiting of the claims.

Non-visual photoreceptors in the human eye (so-called intrinsicallyphotosensitive retinal ganglion cells) are linked to the circadiansystem. While details of the circadian excitation band continue toevolve, a common consensus is that it the excitation band is peaked inthe blue range at around 465 nm.

FIG. 1A is a diagram 1A00 showing a circadian stimulation wavelengthrange (CSWR) 102 as used to tune a circadian-friendly LED light sourceas presented by Brainard et al. in The Journal of Neuroscience, Aug. 15,2001, 21(16):6405-6412 (Brainard), compared to the photopic vision range104. With such a broad effective action spectrum, it appears there islittle one can do to vary circadian stimulation for a white lightsource, other than varying the relative short-wavelength content, thatis, the CCT. However, more recent work suggests that the relevant CSWRis in fact much narrower than presented in Brainard et al. For example,in Rahman et al., Endocrinology, Aug. 7, 2008, 149(12):6125-6135, it isshown that glucocorticoid elevation and melatonin suppression may beavoided by filtering blue light in a wavelength range of only 450 nm to480 nm. This is significant because a narrower CSWR means there shouldbe more flexibility in designing a white light source for desirablequality of light, while also controlling the amount of circadianstimulation. Further, it is noteworthy that Brainard et al. imposed asymmetric shape for their action spectrum when fitting experimentaldata; however, a careful analysis of the experimental points in FIG. 5of Brainard et al. shows that the experimental response at shortwavelength (e.g., 420 nm) is significantly lower than is obtained by thefitted curve. In other words, there is suggestive evidence that the CSWRis not well-known, especially at short wavelength, and may be narrowerthan is reported in some action spectra.

Depending on the details of the actual CSWR at short-wavelength, avariety of light sources with low circadian stimulation can be designed.Therefore it is possible to assume a CSWR and design a light sourceaccordingly. Various embodiments of the invention do this, andillustrate how a light source can be optimized for a given assumed CSWR,for instance by optimizing the tradeoff between circadian stimulationand various aspects of quality of light (including CCT, chromaticity,absence of tint of the white point, and aspects of color rendition) andenergy efficiency.

Circadian stimulation (CS) via ipRGCs for an illuminant with a spectralpower distribution SPD as a function of wavelength, λ, can be modeledas:

${CS} = \frac{\int{{c(\lambda)}{{SPD}(\lambda)}d\; \lambda}}{\int{{{SPD}(\lambda)}d\; \lambda}}$

where c(λ) is the circadian stimulation spectrum. For two illuminants Aand B of equal luminous flux (relevant for illumination applications),the relative Circadian Stimulation (CS) of A vs. B is:

$\frac{{CS}_{A}}{{CS}_{B}} \cdot \frac{{LE}_{B}}{{LE}_{A}}$

where LE is the lumen equivalent of the spectral power distribution.

FIG. 1B shows how the impact of a light source on the circadian systemscales against light intensity. The impact of a light source on thecircadian system scales with relative CS, with light intensity (e.g.,lux level), and with exposure time. One can combine the relative CS andthe data from monochromatic stimuli disclosed by Brainard. One thenobtains FIG. 1B which shows the melatonin suppression for variousilluminances and for various light sources.

FIG. 1B shows melatonin suppression as a function of illuminance (lux)reaching the human eye, after a 90 min exposure. Curve 111 shows theresponse to monochromatic radiation at 460 nm, and is directly takenfrom Brainard. Curve 112 shows the response to standard illuminant D65.Curve 113 shows the response to illumination by standard illuminant A.Curves 112 and 113 are obtained by shifting curve 111, according totheir relative CS.

FIG. 1B shows that for a common indoor residential lighting situation(300 lx under illuminant CIE A, representative of an incandescent lamp)melatonin suppression is significant: about 50% after 90 min. Thus, evenin this common situation the circadian system can be impacted. For lightsources with a larger relative CS than illuminant A, the effect can bestronger.

The following figures and text serve to compare the relative CS betweenvarious LED white light sources. FIG. 1C shows a relative circadianstimulation (CS) for 3300K white light sources composed of a primary LED(varying from violet- to blue-emitting) combined with a green-emittingand a red-emitting phosphor. In FIG. 1C, the x-axis is the centeremission wavelength of the primary LED and the y-axis is the relativecircadian stimulation (normalized to CIE A). The circadian stimulationis calculated assuming a circadian stimulation wavelength range peakedat 465 nm, with a Gaussian line shape and with various full-widthhalf-maxima (from 10 nm to 90 nm) as labeled on the figure (see FIG.1A). Regarding the phosphors used to obtain the white light source,suitable phosphors may be Eu²⁺ doped materials. An example of agreen-emitter is BaSrSiO:Eu²⁺. An example of a red-emitter isCaAlSiN:Eu²⁺. In FIG. 1C, the green and red emission peakwavelength/FWHM are 530/100 and 630/100, respectively. Other phosphorsare also possible, as described below. In addition to phosphors, otherwavelength down-converting materials may be used, such as organicmaterials or semiconductors such as nanoparticles otherwise known as“quantum dots”. In other embodiments, the green and/or red emission maybe provided by LEDs or by laser diodes (LDs). As shown in FIG. 1C, forwide CSWRs (e.g., wide 90 nm 123 and wide 70 nm 124) there is littleprimary LED wavelength sensitivity, or even a penalty as the wavelengthgets too short. However, for narrower CSWRs (e.g., 10 nm 121 and 30 nm122), there is a strong benefit to reducing the primary LED wavelength.For example, for a 30 nm FWHM CSWR 122, the relative CS for a violet(approximately 405 nm to approximately 425 nm) primary 3300K LED isabout half that of the CIE A illuminant (2856K) 125. Thus, light source122 is less circadian stimulating than many incandescent lamps, anddramatically less stimulating than a 445 nm (blue) based 3300K LED 123,which has a CS about 20% higher than CIE A. SPDs for various LED lightsource emissions including those of FIG. 1C are shown in FIG. 1D,normalized to emission at 600 nm. The SPDs are characterized, forexample, by different violet content. For each SPD, CRI is maintained at80 or higher and R9 is above zero (about 10).

Non- or weakly-circadian-stimulating light sources are desirable, forexample, for evening illumination, in order to avoid glucocorticoidelevation and melatonin suppression, and thus prepare people for healthysleep. Referring to the 30 nm FWHM CSWR of FIG. 1C, FIG. 1E shows the CSfor a two-phosphor based LED white light source at 3300K as a functionof the primary LED emission peak wavelength. For a 455 nm primaryemission, the lumen equivalent (LE) of the SPD is high (about 320lm/Wopt), but the CS is also high (about twice that of CIE A). As theprimary LED peak wavelength is reduced below 455 nm, the CS fallsdramatically. Further, as the primary LED peak wavelength is reducedbelow 420 nm, the LE also decreases. Thus, there is a range of primaryLED peak emission wavelengths where the LE is still reasonably high, butthe CS is reduced relative to CIE A. In particular, the wavelength rangeof 405 nm to 435 nm provides reduced CS and reasonable LE. A variety ofstandard LED sources with this CCT have a LE of about 300, thereforeembodiments with an LE of about 200 or about 250 can be consideredacceptable as they provide a much lower CS than standard sources.

FIG. 1F further illustrates the advantage of such light sources. FIG. 1Fshows predicted melatonin suppression versus illuminance at the eyelevel, for a 90 min exposure. Curve 1 corresponds to an LED source with415 nm primary peak emission, and curve 2 corresponds to an LED sourcewith 455 nm primary peak emission. Due to the lower relative CS, the 415nm-primary LED induces less melatonin suppression. If the light level isdimmed to about 100 lux, the suppression becomes very small (less than10% above the ceiling of the signal) whereas for the same illuminanceunder the 455 nm-primary LED, melatonin suppression is significant(about 40% in 90 min). Thus, the change in circadian stimulation has arelevant impact in a realistic environment.

In principle, another approach can be used to reduce the circadianstimulation of a light source: tuning the CCT of the lightsource—indeed, a warmer CCT generally leads to a lower relative CS.Various LED-based products provide this capability. However theseproducts employ blue primary LEDs (peak emission wavelength range fromabout 445 nm to 460 nm). Therefore, even at low CCT, the relative CSremains fairly high (e.g., about twice that of illuminant CIE A for a3000K LED source, as shown, for example, in FIG. 1C).

Therefore, careful choice of the emission wavelength of the primary LEDand of the overall emission spectrum of the primary LED is important tosignificantly modulate CS.

Embodiments of various circadian-friendly LED white light sources can beconfigured such that the respective emission spectra can be tuned so asto simulate a circadian cycle in a more or less daily diurnal cycle.

FIG. 2A shows spectral power distributions (SPDs) of various wavelengthcombinations 2A00 as used in configuring a circadian-friendly LED whitelight source.

As shown in FIG. 2A, a stimulating blue peak is emitted for morningcircadian stimulation (see curve 202). Another curve exhibits lowcircadian stimulation (see curve 206) for evenings, and a third curve(204) shows an intermediate option.

In certain embodiments, a circadian-friendly LED white light source(e.g., see luminaire of FIG. 4A and lamp of 6A and FIG. 6B) includes afirst LED (see FIG. 2B) such as a violet (or UV) primary LED combinedwith a green, red, and (optional) blue phosphor to emit a spectrum 208that is substantially a low-circadian-stimulating spectrum at acorrelated color temperature (CCT) of 2500K (see spectrum of LEDemissions 208 in FIG. 2B). Such an LED and phosphor combination canexhibit a reasonable white color point and can exhibit reasonable colorrendering properties. Depending on the details such as the emissionspectra of the primary LED and phosphors, it may not be necessary tocombine a blue phosphor with a first LED.

For implementation of a circadian-friendly LED light source, a secondLED (see FIG. 2C) can be added. The emission 210 (FIG. 2C) can begenerated by using a second LED comprising, for example, a violet (orUV) LED to pump only a blue phosphor. The blue phosphor can be selectedbased on absorption characteristics of photons from the primary (violetor UV) LED: namely, is the blue phosphor can be chosen such thatexcitation can occur for moderate phosphor loading, such that theresulting system package efficiency is sufficient. Also, a blue phosphorcan be selected based on the emission properties of the combination soas to combine with the first LED emission, thus shifting or tuning thechromaticity in a controlled manner (e.g., in a direction similar toincreasing CCTs along the Planckian curve to maintain a white lightappearance). In addition, a blue phosphor peak emission wavelength andFWHM can be selected to maintain specified color rendering propertieseven as the contribution of the second LED to the total spectrum (firstand second LED combined) is increased (FIG. 2A). In some cases, thedesired color rendering properties can be expressed as a CRI above 50, aCRI above 80, or in certain embodiments, a CRI above 90. Other metricssuch as R9, another color fidelity metric, and/or a color gamut metriccan also be employed. In some embodiments, a blue phosphor may be a mixof different phosphors, which, combined together, give the desiredexcitation and emission properties including the desired dominantwavelength of emission for spectral tuning as described herein.

For an SPD with a CCT of 2500K, the fraction of power in the spectralrange from 400 nm to 440 nm is 0.03 and the fraction of power in therange from 440 nm to 500 nm is 0.06. For an SPD with a CCT of 5000K, thefraction of power in the spectral range from 400 nm to 440 nm is 0.02and the fraction of power in the range from 440 nm to 500 nm is 0.20.

Certain color rendering properties for LED white light sources providedby the present disclosure at various LED temperatures are illustrated inFIG. 3A. The circadian stimulation (relative to a CIE A illuminant),based on a CSWR modeled after Brainard (102 in FIG. 1A, about 95 nmFWHM) is illustrated in FIG. 3B.

Certain embodiments use a blue phosphor characterized by a 477 nm peakemission wavelength and a FWHM of 80 nm. Such blue phosphors with a 477nm peak emission wavelength represents only one embodiment and otherembodiments use other phosphors and phosphor combinations. Inparticular, the phosphors and/or compositions of wavelength-conversionmaterials referred to in the present disclosure may comprise variouswavelength-conversion materials.

Wavelength conversion materials can be crystalline (single or poly),ceramic or semiconductor particle phosphors, ceramic or semiconductorplate phosphors, organic or inorganic downconverters, upconverters(anti-stokes), nano-particles and other materials which providewavelength conversion. Major classes of downconverter phosphors used insolid-state lighting include garnets doped at least with Ce³⁺;nitridosilicates, oxynitridosilicates or oxynitridoaluminosilicatesdoped at least with Ce³⁺; chalcogenides doped at least with Ce³⁺;silicates or fluorosilicates doped at least with Eu²⁺; nitridosilicates,oxynitridosilicates, oxynitridoaluminosilicates or sialons doped atleast with Eu²⁺; carbidonitridosilicates or carbidooxynitridosilicatesdoped at least with Eu²⁺; aluminates doped at least with Eu²⁺;phosphates or apatites doped at least with Eu²⁺; chalcogenides doped atleast with Eu²⁺; and oxides, oxyfluorides or complex fluorides doped atleast with Mn⁴⁺. Some specific examples are listed below:

-   -   (Ba,Sr,Ca,Mg)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺, Mn²⁺    -   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺, Mn²⁺    -   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺, Mn²⁺    -   (Na,K,Rb,Cs)₂[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   (Mg,Ca,Zr,Ba,Zn)[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   (Mg,Ca,Sr,Ba,Zn)₂SiO₄:Eu²⁺    -   (Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺    -   (Ca,Sr)S:Eu²⁺,Ce³⁺    -   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Sc,Al,Ga)₅O₁₂:Ce³⁺    -   Eu_(x)(A1)_(6−z)(A2)_(z)O_(y)N_(8-z)(A3)₂(_(x+z−y)), where        0≤z4.2; 0≤y≤z; 0≤x0.1; A1 is Si, C, Ge, and/or Sn; A2 is Al, B,        Ga, and/or In; A3 is F, Cl, Br, and/or I.

The group:

Ca_(1−x)Al_(x−xy)Si_(1−x+xy)N_(2−x−xy)C_(xy) :A   (1);

Ca_(1−x−z)Na_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A   (2);

M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A  (3);

M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy−2w/3)C_(xy)O_(w-v/2)H_(v):A  (4); and

M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy−2w/3-v/3)C_(xy)O_(w)H_(v):A  (4a),

-   -   wherein 0<x<1, 0<y<1, 0≤z<1, 0≤v<1, 0<w<1, x+z<1, x>xy+z, and        0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at        least one monovalent cation, M(III) is at least one trivalent        cation, H is at least one monovalent anion, and A is a        luminescence activator doped in the crystal structure.    -   Ce_(x)(Mg,Ca,Sr,Ba)_(y)(Sc,Y,La,Gd,Lu)_(1−x−y)Al(Si_(6+y)Al_(z−y))(N_(10−z)O_(z))        (where x,y<1, y≥0 and z˜1)    -   (Mg,Ca,Sr,Ba)(Y,Sc,Gd,Tb,La,Lu)₂S₄:Ce³⁺    -   (Ba,Sr,Ca)_(x)Si_(y)N_(z):Eu²⁺ (where 2x+4y=3z)    -   (Y,Sc,Lu,Gd)_(2−n)Ca_(n)Si₄N_(6+n)C_(1−n):Ce³⁺, (wherein        0≤n≤0.5)    -   (Lu,Ca,Li,Mg,Y) alpha-SiAlON doped with Eu²⁺ and/or Ce³⁺    -   (Ca,Sr,Ba)SiO₂N₂:Eu²⁺,Ce³⁺    -   (Sr,Ca)AlSiN₃:Eu²⁺    -   CaAlSi(ON)₃:Eu²⁺    -   (Y,La,Lu)Si₃N₅:Ce³⁺    -   (La,Y,Lu)₃Si₆N₁₁:Ce³⁺    -   (Mg,Ca,Sr,Ba)(S,Se):Eu²⁺    -   Sr[LiAl₃N₄]:Eu²⁺.

For purposes of the application, it is understood that when a phosphorhas two or more dopant ions (i.e., those ions following the colon in theabove phosphors), this is to mean that the phosphor has at least one(but not necessarily all) of those dopant ions within the material. Thatis, as understood by those skilled in the art, this type of notationmeans that the phosphor can include any or all of those specified ionsas dopants in the formulation. Further, it is to be understood thatnanoparticles, quantum dots, semiconductor particles, and other types ofmaterials can be used as wavelength converting materials. The list aboveis representative and should not be taken to include all the materialsthat may be utilized within embodiments described herein.

More discussion of suitable phosphors for specific embodiments will bepresented further in this application.

Embodiments of lamps can include any of the aforementioned wavelengthconversion materials, and can exhibit various qualities of lightcharacteristics. Some of such qualities of light characteristics areshown in FIG. 3A and FIG. 3B.

FIG. 3A is a color rendering chart 3A00 showing color rendering index(Ra) and red color rendering (R9) exhibited by a circadian-friendly LEDwhite light source of FIG. 2A at three different color temperatures(e.g., 5000° K, 3500° K, and 2500° K).

When the first and second LED emissions are combined in comparablelevels, a 5000K color point can be achieved with acceptable colorrendering (Ra, R9 of 80, 65 respectively). Moreover, this emissionspectrum can have a high relative circadian stimulation (as definedabove) similar to that achieved with a D65 reference illuminant(daylight). When the second LED emission is reduced to a very low level(or turned off), the first LED emission dominates, and alow-circadian-stimulating spectrum is achieved at 2500K with Ra, R9 of93, 65. At an intermediate point, a 3500K color temperature is providedwith Ra, R9 of 85, 88 and a mid-level stimulation of the circadiansystem. Accordingly, this LED white light source can be used to achievehigh-stimulating 5000K light in the morning, 3500K mid-stimulatingillumination in the afternoon, and low-stimulating 2500K light in theevening, all while maintaining acceptable white light quality (Ra≥80,R9≥50). Total power to the first and second LEDs may be adjusted toprovide the desired total illuminance levels.

FIG. 3B is a chart 3B00 showing relative circadian stimulation resultingfrom a circadian-friendly LED light source.

FIG. 3B shows the relative circadian stimulation of thecircadian-friendly light source illustrated in FIG. 2A, using a 95 nmFWHM CSWR as modeled after Brainard. By combining both first and secondLED emissions to achieve a color temperature of 5000K (202 in FIG. 2A),a very high circadian stimulating effect is achieved. As shown in FIG.3B, at 5000K the relative circadian stimulation is approximately 2.8times higher than that of the CIE A reference illuminant. This level ofcircadian stimulation is close to that achieved with an illuminantassociated with daylight (e.g., D65 illuminant, as shown), which has arelative circadian stimulation 3.1 times higher than that of the CIE Areference illuminant. When the second LED is turned down (or off) sothat the first LED emission dominates, the 2500K spectrum is achieved(206 in FIG. 2A), which has a very low circadian stimulation (within 10%of that of the CIE A reference illuminant). When the intensity of thefirst and second LED emission are comparable, an intermediate spectrumat 3500K is achieved (204 in FIG. 2A), which provides a relativecircadian stimulation about two times higher than that of the CIE Areference illuminant.

The color may be changed dynamically (either continuously or stepwise)throughout the day, via a clock-controlled driving scheme. Or, thedesired color point may be selected using a switching mechanism providedfor the end user. Many other automatic and/or human-interface controlschemes may be employed, such as power-line communication, Wi-Fi, Zigby,DALI, etc. Different target CCTs are also possible. It is expected thatsuch a light source would have dramatic benefits for health and amenitycompared to circadian-unfriendly light sources such as standardblue-based LEDs.

FIG. 4A shows an example of a light strip used to implement a whitelight source that is tunable based on measurable aspects (e.g., time ofday) and/or changes in the environment. Such a white light source can beformed, for instance, by mixing at least two LED-based sources: e.g., afirst using an appropriate mix one set of red-, green- and (optional)blue-emitting phosphors with violet-primary LEDs, and a second usingeither violet-pumped blue phosphor LEDs or blue-primary LEDs. The twosources can be mixed throughout a diurnal cycle to form acircadian-friendly LED white light source. Such a light strip may beused, for example, as a light engine for a linear troffer luminaire.

In other embodiments, the CSWR can be narrower than described byBrainard (curve 401 in FIG. 4B). For example, consider a 465 nm peakGaussian CSWR with a FWHM of 30 nm as shown as curve 402 in FIG. 4B. Forthis narrower CSWR, it is possible to design LED white light sourceshaving a CCT higher than that of CIE A, but with lower circadianstimulation.

FIG. 4C shows a first LED emission 4C100 of a violet-primary LED pumpinga green and red phosphor 403. This emission is at 3286K but has a CS 50%relative to CIE A. Thus, the LED white light source has a higher CCTthan CIE A but a lower circadian stimulation. The second LED emission4C200 (FIG. 4C) is a violet primary LED pumping a blue phosphor having apeak emission wavelength of 477 nm 404. The first and second LED-basedemissions can be combined, as shown in FIG. 4D, to tune from about 5000Kto about 3300K, varying the CS from about 300% to less than 50% that ofCIE A, while maintaining a white point within 4 points of the Planckian,a CRI>80, and an R9>10, as shown in the table in FIG. 4D.

This change in CS can also be quantified by considering the relativespectral content (e.g., fraction of the SPD) in specific spectralranges. Two ranges of interest are the relative spectral content in the‘violet-blue’ (VB) range 400 nm to 440 nm and in the ‘blue-cyan’ (BC)range 440 nm to 500 nm. The former range is relatively lesscircadian-stimulating, and the latter range is relatively morecircadian-stimulating. The table in FIG. 4D shows the relative spectralcontent for these wavelength ranges. When tuning from 5000K to 3300K,the fraction of total SPD power in the VB range increases slightly (from0.19 to 0.23) whereas the fraction in the BC range decreasessignificantly (from 0.20 to 0.05). This re-apportioning of the spectralcontent from the BC range to the VB range contributes to the low CS ofthe 3300K SPD. Also, note that the presence of violet light enables theSPD to remain on-Planckian.

It is an unexpected result that it is possible to design a SPD having asmall amount of blue light (to reduce the CS significantly against astandard light source, such as illuminant A) while also retaining goodproperties: high CRI and R9, chromaticity on-Planckian, good LER. Indeedit is conventionally believed that the presence of blue light isnecessary to achieve on-Planckian white balance, and that the use ofviolet light instead of blue light has a prohibitive impact on LER.

In certain embodiments, having a large fraction Fv of the SPD in the VBrange or a small fraction Fc in the BC range corresponds to a low CS,and vice-versa. For example, an SPD characterized by a Fc>0.1 may have ahigh stimulation, and an SPD characterized by a Fc<0.06 and Fv>0.05 mayhave a low stimulation. Similarly, an SPD characterized by a Fc/Fv>0.5may have relatively high stimulation, and an SPD characterized by aFc/Fv>1 may have a high stimulation. An SPD characterized by a Fc/Fv<0.4may have a relatively low stimulation and an SPD characterized by aFc/Fv<0.2 may have a low stimulation. These ranges correspond to certainembodiments of LED white light sources provided by the presentdisclosure, including those of FIGS. 4A-4N and FIGS. 5A-5C.

Therefore, the CS can, in general, be proportional to the ratio Fc/Fv,with higher values being associated with greater circadian stimulation.CS can also, in general, be proportional to the Fc content. Furthermore,in certain embodiments, increasing the VB content of a LED white lightsource will decrease the BC content, and conversely increasing the BSwill result in reduced VB content.

Fv and Fc represent the fraction of power in the SPD within either theVB wavelength range or the BC wavelength range, respectively. Forexample, where the total power in the SPD is 1, when 10% of the power inthe SPD is in the VB wavelength range, Fv is 0.1; and when 10% of thepower of the SPD is in the BC wavelength range, Fc is 0.1.

In certain embodiments, Fv is less than 0.2, less than 0.15, less than0.1, less than 0.08, and in certain embodiments, less than 0.05.

In certain embodiments, Fv is greater than 0.2, greater than 0.15,greater than 0.1, greater than 0.08, and in certain embodiments, greaterthan 0.05.

In certain embodiments, Fc is less than 0.2, less than 0.15, less than0.1, less than 0.08 and in certain embodiments, less than 0.05.

In certain embodiments, Fc is greater than 0.2, greater than 0.15,greater than 0.1, greater than 0.08, and in certain embodiments, greaterthan 0.05.

Various combinations of Fv and Fc can be provided consistent withproviding a LED white light source of the present disclosure. It issignificant that using the devices and methods provided by the presentdisclosure, Fv, i.e., the spectral content in the VB range from 400 nmto 440 nm can be controlled to provide a desired white light emissionand maintain desired attributes such as CCT, CRI, Ra, Duv, and others.Use of violet emitting LEDs and select phosphors, and optionallyadditional LEDs emitting at other wavelengths, provide the ability tomore accurately control the content in the VB range from 400 nm to 440nm.

In certain embodiments, Fc/Fv is from 0.1 to 1, from 0.1 to 0.8, from0.1 to 0.6, and in certain embodiments, from 0.1 to 0.4.

In certain embodiments, Fc/Fv is less than 0.1, less than 0.2, less than0.3, less than 0.4, less than 0.5, and in certain embodiments, less than0.6.

In certain embodiments, Fc/Fv is from 0.5 to 1.5, from 0. 5 to 1.3, from0.5 to 1.1, and in certain embodiments, from 0.5 to 0.9.

In certain embodiments, Fc/Fv is greater than 0.5, greater than 0.6,greater than 0.7, greater than 0.8, greater than 0.9, and in certainembodiments, greater than 1.

It should be appreciated that it is not trivial to obtain the highquality of light demonstrated by the embodiments of the presentdisclosure. Although one can reduce the CS of a light source by simplyremoving all (or most) of the blue and cyan emission—withoutsupplementing it with violet radiation, the resultant color renderingindex would be poor because of the absence of short-wavelength light inthe spectrum. Furthermore, it can be difficult to maintain thechromaticity of a source near-Planckian (resulting in a source with alow CCT and/or a greenish tint). In contrast, embodiments of the presentdisclosure balance the amount of blue and violet light and therebyfacilitate modulating the CS while maintaining high quality of light(e.g., CRI, Ra, Duv).

It is possible for a second LED emission to use a primary blue-emittingLED with a suitable dominant wavelength to tune along the Planckian. Forexample, as shown in FIG. 4E, an about 480 nm peak emission LED may beused in place of the blue-phosphor-based LED of FIG. 4C. FIG. 4E showsan emission spectrum of a first LED-based source 420 and FIG. 4E shows aspectrum 421 of a blue-emitting LED. By combining the emissions shown inFIG. 4E, a similar effect is achieved as shown by the combined spectrum422 in FIG., with slight differences in color properties and levels ofcircadian stimulation, as shown in the table in FIG. 4F.

In the case of a 465 nm peak Gaussian CSWR with a FWHM of 30 nm, it isillustrative to compare the relative CS for common light sources withLED white light sources provided by the present disclosure. FIG. 4Gshows the CS (normalized to that for CIE A) as a function of colortemperature for common light sources such as candlelight (1850K), CIE A(2856K), D50 phase daylight (5000K), and D65 phase daylight (6500K). TheCS varies from about 25% (candlelight) to almost four times (D65) thatof CIE A. Also plotted are the CS for a 455 nm blue primary LEDtwo-phosphor 3000K LED, and that for a 425 nm violet primary LEDtwo-phosphor 3000K LED. The difference in circadian stimulation isremarkable, with that for the 455 nm-based LED white light source beingmore than 1.5-times higher than that of CIE A, and more than three timesthat of the 425 nm-based LED white light source. It is worth noting thatCe³⁺ garnet phosphors (e.g., “YAG”) are not highly absorbing in theviolet, so for the 425 nm-based LED it may be desirable to use a Eu²⁺phosphor for the green, as well as for the red, emissions.

FIG. 4H shows light strip having two different sets of LED-basedemitters and a clock/timer, control circuits 4H01, and a driver tocontrol the ratio of emissions of the two different sets of LED-basedemitters to implement a circadian-friendly LED white light source,according to some embodiments.

As shown, a first group of violet-primary LEDs with an appropriate mixof red-, green- and (optionally) blue-emitting phosphors 4H02 can becombined with a second group of violet-primary LEDs with blue phosphors,or blue-primary LEDs, 4H04.

The first and second groups of LED-based emitters may be contained inseparate packages, and the light combined with mixing optics, or theLED-based emitters may be incorporated into a single package, such as as chip-on-board (COB) package (e.g., see the arrangement of FIG. 8)and/or linear COB packages. COB packages can be used in a lamp assemblyas is shown in FIG. 6A and FIG. 6B.

In addition, although the above embodiments describe two-channel tuningmethods to provide varying levels of circadian stimulation whilemaintaining a high quality of light, which can be useful to minimizecost and complexity, it is possible to use three or more channels usingthe devices and concepts provided disclosure. More channels offer moredegrees of freedom in terms of light source selection, and tuning forarbitrary (e.g., non-linear) curves in chromaticity space, but at thecost of higher levels of complexity in terms of luminaire design, LEDprocurement, mixing, and control.

In addition to the elements shown in FIG. 4H one or more light mixingoptics (not shown) may be used to mix the LED emissions first group andsecond group to provide a uniform or other desired light colorappearance. Still further, secondary optics can be used to achieve adesired light distribution pattern.

The foregoing discussion is focused on lighting systems and benefitsresulting from a reduced CS. However, display systems can also benefitfrom a reduced CS.

FIG. 4I shows measured SPDs 4I00 for two display systems with a whitescreen—a laptop screen 402 and a smartphone screen 404. Examples ofother display systems are illustrated in FIGS. 15D through 15E. Bothdisplays shown in FIG. 4I have CCTs of about 6500K, which is typical fordisplay screens. Both are lit by blue-primary LEDs and the emissionspectra are characterized by a large blue peak. The relative circadianstimulation is about 330% for the laptop and about 470% for the phonescreen.

FIG. 4J shows the predicted melatonin suppression 406 (after 90 minexposure to a white screen of a smartphone) versus luminance for thesmartphone screen. In practice, luminance levels for displays can behigh—one hundred to several hundreds of lux in some cases (for instanceif the device is held close to the face). Therefore, the net impact onthe circadian system can be significant and can disrupt sleep patterns,even for a relatively short exposure time.

For display applications, there are already software solutions that aimat reducing circadian disruption. For instance, software such as “flux”can adapt the CCT of the screen with time: during the day, the CCT isabout 6500K, but as the night falls the CCT is ‘warmed’ to about 3400K.

FIG. 4K shows an example of a spectrum emitted by a white screen usingthis software: curve 410 is for the standard emission (6500K) and curve408 is for the warmed emission (about 3400K nominally).

The reduction in CCT is beneficial because the relative circadianstimulation is less at lower CCT. Namely, the relative circadianstimulation is about 330% for the standard emission and about 210% forthe warmed screen (assuming equal luminance), relative to illuminant A.While this is an improvement, stimulation is still high for the warmedscreen due to the use of blue-pump LEDs. Also, it can be useful toreduce CS while still achieving the more typical electronic displaywhite center point (typically 6000K to 7000K).

Therefore, as with lighting systems, a careful choice of the emissionwavelength and profile of the primary LED and of the overall SPD isimportant to obtain a display system with a low circadian stimulation.

FIG. 4L illustrates relevant spectra for typical LED-lit liquid crystaldisplays (LCD), which are used in many applications includingtelevisions, monitors, laptop and notebook computers, gaming systems,and portable devices such as tablets, phones, MP3 players, etc. FIG. 4Lshows spectra for a blue color filter 412, a green color filter 414, anda red color filter 416 (collectively, CFs) which are employed inconjunction with an LCD display to control color. A typical LED spectrum(e.g., LED spectrum 418) is a blue primary-based LED pumping a yellow(and/or red) emitting phosphor system. Filtering by the red, green andblue filters results in a transmitted spectrum, for example, a whitetransmitted spectrum 419 if all three filters fully transmit. A typicalcolor gamut of this system (shown as triangle 426 in FIG. 4L) is limitedin the green and red, and covers an area in x-y chromaticity space ofabout 79% with respect to the National Television System Committee gamutstandard 422 (NTSC, 1953). As discussed above, such an LED-based source(with a primary peak wavelength typically in the 440 nm to 460 nm range)is inherently highly circadian stimulating, which can be undesirableespecially for viewing in the evenings and nighttime. FIG. 4L also showsthe Planckian locus 424 and the boundaries of the (xy) colorspace 420.

FIG. 4M shows the calculated relative CS (curve 430) and relativedisplay efficacy (curve 428) as the “blue” LED primary peak wavelengthis decreased (using the same phosphor emission, while maintaining thesame display white color point), using a 465 nm peak Gaussian CSWR witha FWHM of 30 nm. For peak wavelengths less than 440 nm, there is asignificant drop in CS, which reaches a minimum at about 410 nm. Theefficacy reduces also, but more slowly with decreasing peak wavelength,suggesting an optimum peak wavelength range between 410 nm and 440 nm orbetween 420 nm to 430 nm for a reduced-CS display.

FIG. 4N shows embodiments for which the phosphor system is tuned tobetter work with a chosen primary peak emission wavelength of 425 nm. InFIG. 4N, 83% NTSC is achieved using phosphors with peak/FWHM (emission)of 530 nm/85 nm and 605 nm/80 nm, with only about a 10% efficacy penaltycompare to a 450 nm-based source achieving 79% NTSC. In FIG. 4N, 90%NTSC is achieved using phosphors with peak/FWHM (emission) of 530 nm/85nm and 630 nm/80 nm, with only about a 20% efficacy penalty compare to a450 nm-based source achieving 79% NTSC. One skilled in the art canidentify different combinations of phosphors to achieve the desiredbalance of color gamut and efficacy. Use of a 425 nm wavelength primaryLED can reduce CS by about five times, which is extremely significant.Referring to FIG. 4J, a five times reduction for a 100 lux display wouldreduce melatonin suppression from about 50% to about 20% for a 90 minuteexposure.

Application of the present disclosure is not limited to displays basedon LCDs. Direct-view LED displays have been demonstrated, using bothorganic and inorganic LEDs. In these displays individual pixels are madeup of active LEDs, which include blue, green, and red emitters and areselectively controlled. Based on embodiments of the present disclosure,the “blue” emitters may be tuned to shorter wavelengths to reduce CS asdescribed. In certain embodiments, using a 465 nm peak Gaussian CSWRwith a FWHM of 30 nm, an optimum peak wavelength range for the “blue”emitter can be between 410 nm and 440 nm, or between 420 nm and 430 nm,can be chosen for a reduced-CS display.

It is also possible to mix longer and shorter wavelength primary “blue”LEDs in order to have displays in which CS can be controlled. Forexample, it may be desirable to have high CS stimulation in the morning(e.g., 440 nm to 460 nm primary “blue”) that shifts to shorterwavelength (e.g., 420 nm to 430 nm) during the evening. This can be doneby including two sets of primary “blue” LEDs in the display and can beimplemented in both LCD and direct-view LED-based displays.

In some cases the color point (or more generally the spectrum) of theembodiments can be tuned automatically in response to behavior oractions of the end user. Examples of such trigger events include thepresence of the end user in a room (or a part of the room) for a givenamount of time, the movement of the user across the space, the user'sgeneral level of activity, specific words or gestures, and/or actions ona device (a smartphone for instance). Such responses may be employed tomatch the spectrum to the condition of the user (for instance, lower thecircadian cycle when the user becomes sleepy or prepares for sleep) orto modify the condition of the user (e.g., detect sleepiness andincrease circadian stimulation to lessen it). In some cases, theresponse can be determined by the user's behavior in combination withother measurable conditions or cues such as time of the day, weatherand/or changing weather, amount of outdoor light, etc. In some cases,the cues can be obtained from another “smart” system (another appliance,a smartphone, or other electronic device) which monitors the user'sbehavior—the cues can then be communicated over a network (wired orwireless) between said smart system and the lighting system, such as anetwork enabled by a smart-home hub. In some cases the cues relate tothe user's past behavior, such as the time the user woke up or his pastsleep pattern, which has been recorded by a system such as the user'ssmart phone.

In some cases, a response can be predetermined by the manufacturer ofthe system so that a given set of cues leads to a deterministicresponse. In other cases, the lighting system “learns” from the user.For instance, in a teaching phase, the user (or another person) manuallytunes the spectrum. The system learns to associate these settings withspecific cues and the tuning is then performed automatically in responseto the cues, (e.g., rather than being triggered manually). Learning canbe achieved by a variety of machine-learning techniques known to thoseskilled in the art, such as via a neural network and/or using Bayesianinference.

A specific example of the previous scenario is as follows: The userfollows a routine (e.g., a series of actions performed repeatedly withsome periodicity) a few hours before going to bed. Such a routine mightinclude leaving the dining table, brushing his teeth, watching TV etc.Cues of this routine are collected by various appliances (TV,toothbrush, motion sensors) and communicated with the lighting systemthrough a wireless protocol. In the teaching phase, the user also tunesthe spectrum of the lighting system to reduce circadian stimulation—forexample, the user the lighting system to a non-stimulating setting a fewhours before going to bed. Once the system has associated these settingswith one or more cues of the routine, and with an approximate hour, thetuning occurs automatically to help reduce the circadian response beforethe user goes to bed. Conversely, tuning can also occur in the morningto stimulate the circadian system.

Such automated behavior can be used for a variety of light-emittingsystems—including lighting appliances per se, and for display systems(e.g., TV and computer screens, tablets, phones, etc.). Such lightingsystems may for instance adapt their spectrum to reduce circadianstimulation a given time before the user goes to bed. In the case ofdisplay systems, the change in LED spectrum may be combined withsoftware changes (such as the screen's color point) in order to furtherreduce circadian stimulation. Such automated behavior can be implementedin a wide variety of lighting situations. Strictly as one example, alight strip can be fitted with sensors to take-in and/or learn frommeasurable aspects and/or changes in the environment, and in response,tune circadian-friendly emissions.

While the previous examples assumed a domestic setting, such embodimentswith automatic or ‘smart’ tuning can be used in other contexts such asin a professional context. For example, in an office setting, thelighting system may adapt to monitor used activity and increase CSaccordingly; or the CS may be increased in the morning, reduced near theend of the work day, or adapted to complement the outside lightingconditions (which could vary with weather and season). System tuning mayfollow a simple timing scheme or also take into account the workers'behavior. Embodiments may also be used in other contexts where sleeppattern is affected, including night-shift worker facilities, long-rangetravel (such as airplane flights), care facilities for the elderly.

Further, in various cases, the intensity of the light emitted by thesystem may be tuned together with its spectrum to further influence CS.For instance, the intensity may be dimmed as the spectrum is tuned forlower CS. In the case of a display, the luminance of the display may bedimmed and its CS may be lowered if the ambient light in the roomdecreases—this can be detected by a simple light sensor connected to thedisplay.

FIG. 5A is a chart 5A00 showing a linear chromaticity curve 502 producedby a circadian-friendly LED white light source in x-y chromaticityspace. FIG. 5A also shows the Planckian loci 510 and minimum-hue-shiftcurve 512 as described by Rea and Freyssinier, Color Research andApplication 38, 82-92 (2013).

The Planckian loci form a curve in chromaticity space, leading to thepopular notion that a linear dual-track tunability cannot properlyreplicate white emission across a wide range of color temperatures.However, recent psychophysical experiments show that the definition of“white” may deviate from the Planckian curve. In particular, subjectstend to observe less tint for color points below the Planckian loci.

This observation has two ramifications: 1) a person's perception of“white” is somewhat arbitrary, and 2) tinting below the Planckian curvemay not only be acceptable, but perhaps preferred. Opening up thisregion in chromaticity space allows for the engineering of dual-channeltunable white emission. The chromaticities for the three colortemperatures described for a circadian friendly light-source (FIG. 2A)are shown (e.g., see point 504, point 506, and point 508) superimposedon the Planckian loci and the “minimum-hue-shift” points. Based on thearguments above, these three color points (and those in between) canprovide an acceptable white appearance, as well as good color renderingproperties.

Again this is not trivial to achieve because the most obvious way toreduce the CS of a light source is to remove blue or cyan light, thusshifting the chromaticity above the Planckian (and away from thepreferred chromaticity curve 502 shown in FIG. 5A).

FIG. 5B is a chart 5B00 showing the shape of a white light boundingregion 514 as produced by a circadian-friendly LED white light source,according to some embodiments. The white light bounding region 514 istaken as the range limits of the Planckian loci 510 and“minimum-hue-shift” curves, inclusive of a ±0.005 border region in x-ychromaticity space.

As shown in FIG. 5B, the white light bounding region is highlighted withhatching. In particular, the hatched region 514 represents varyingratios of color mixing, and bounds of a white light region.

In yet other embodiments, the change in circadian stimulation is notassociated with a change in CCT or chromaticity. This can be useful insituations for which a given CCT (e.g., 3000K or 6500K) is desired atall times, but the stimulation should vary through the day. This can beuseful for lighting applications and for display applications, where CSmay be changed without the user being aware in a change in illumination.Such embodiments may, for example, be achieved by combining twoLED-based tracks emitting light with a CCT of 3000K. One track can havea large relative circadian stimulation, and the other can have a lowcircadian stimulation. More specifically, the first track may includeblue pump LEDs and phosphors and the second track may include violetLEDs and phosphors. As disclosed herein, the emission spectrum from eachtrack can also be designed to provide high quality of light (e.g., a CRIabove 80). In such systems, it may be desirable to design the spectrasuch than their chromaticities are similar perceptually rather thannominally. Alternatively, it may be desirable to compute thechromaticities with suitable color matching functions (CMFs) such as the1964 CMFs or other modern CMFs, rather than the conventional 1931 2degree CMFs. This is because the predictions of the 1931 2 degree CMFsare sometimes poorly representative of user perception. In addition,chromaticity calculations may be performed for a given demographic group(e.g., taking into account the reduction of sensitivity toshort-wavelength light for elderly users).

Such embodiments, with a stable CCT, are illustrated in FIG. 5C, inwhich two sets of LED-based sources are controlled independently: (1) ablue primary based LED white source at 3300K with CRI about 80 and R9greater than 0 (“BLED” 502), and (2) a violet primary based LED whitesource at 3300K with CRI about 80 and R9 greater than 0 (“VLED” 504).When the BLED devices are on and the VLED off, the circadian stimulationis high (210% of CIE A). Alternatively, When the VLED devices are on andthe BLED off, the circadian stimulation is low (54% of CIE A). In mixedcombinations, the circadian stimulation varies between these two levels;however, the chromaticity is nominally unchanged. In other embodimentsthe primary blue LEDs could be replaced by blue phosphors pumped byshorter wavelength LEDs. FIG. 5C2 shows the CIE 508 for an LED-basedwhite light source described above and FIG. 5C3 shows an example of thecombined VLED and BLED spectrum 506. The CS for representative BLEDfractions is provided in FIG. 5C4.

Here again, the change in CS can also be related to a change in relativespectral content (e.g., fraction of the SPD) Fv in the ‘violet-blue’(VB) range 400 nm to 440 nm and Fc in the ‘blue-cyan’ (BC) range 440 nmto 500 nm. Referring to FIG. 5C1, for SPD 502, Fv=0.01 and Fc=0.14 andfor SPD 504 Fv=0.24 and Fc=0.05.

In certain embodiments, an LED emission source is characterized by acolor rendering index above 80; a Fv of at least 0.01, at least 0.05, atleast 0.1, at least 0.15, at least 0.2, and in certain embodiments, atleast 0.25; and an Fc of at least 0.01, at least 0.05, at least 0.1, atleast 0.15 at least 0.2, at least 0.25, at most 0.01, at most 0.05, atmost 0.10, at most 0.15, at most 0.20 or at most 0.25; or a combinationof any of the foregoing.

FIG. 6 shows an exploded view 600 of an assembly view 6B00 of an LEDlamp forming a circadian-friendly LED light source.

As shown in FIG. 6, the exploded view 600 includes a GU10 (10 mm“twist-lock”) base for connecting to a 120/230-volt source. Such anembodiment can be used as an MR16 halogen light replacement 6B00 for the35/50 watt halogen lamps in use since the mid-2000s.

The lamp shown in FIG. 6 is merely one embodiment of a lamp thatconforms to fit with any one or more of a set of mechanical andelectrical standards.

The list above is representative and is not intended to include all thestandards or form factors that may be utilized with embodimentsdescribed herein.

FIG. 7 shows a schematic of a multi-track driver control system as usedin an LED lamp employing a circadian-friendly LED light source. As shownin FIG. 7, the emission of multiple strings of LEDs is separately variedsuch that the ratio of output of one string with respect to anotherstring is varied according to a time-based function. For example, theclock/timer can model the sunrise and sunset timings over a 24-hourperiod, and during the 24 hour period, a violet emitting LED with bluephosphor can be attenuated in afternoon and evening hours. In dual tracksystems, a linear chromaticity curve 502 can be implemented. With threeor more tracks (e.g., the shown three groups of LEDs) non-linearchromaticity curves can be enabled. Suitable driver control systems aredisclosed in U.S. Application No. 62/026,899 filed on Jun. 25, 2014,which is incorporated by reference in its entirety.

Control circuits (e.g., control modules) can employ any known-in-the-arttechniques, including current limiting based on current or voltagesensing, and/or current limiting based on temperature sensing. Morespecifically, one or more current limiters (e.g., current limiter 704)can be controlled by any known techniques. The controller and/or currentlimiters in turn can modulate the current flowing to any individualgroups of LEDs (e.g., Group1 LEDs 706, Group2 LEDs 708, GroupN LEDs 709,

etc.), which current flowing to any individual groups can beindividually increased or decreased using FETs or switches (e.g., SW1710, SW2 712, SW3 714, etc.). The shown control circuits 719 compriseenvironmental sensors, and a clock/timer, each of which provide inputsto controller 721, which in turn serves to modulate the current flowingto any individual groups of LEDs (e.g., Group1 LEDs 706, Group2 LEDs708, GroupN LEDs 709, etc.).

FIG. 8 shows two strings of LEDs in an intermixed physical arrangement802 to form a two-channel, circadian-friendly arrangement 800 as used inan LED lamp. As shown, the control circuits can employ anyknown-in-the-art techniques to independently modulate the currentflowing to either of the shown groups of LEDs (e.g., Group1 LEDs 706,Group2 LEDs 708).

Each of the Group1 LEDs, and Group2 LEDs comprise individualpatterned-phosphor chips so that the circadian-friendly source may becondensed into a compact area, for example, for directional lighting. Amixing optic can be included to mix the two types of LED light emissions(e.g., for homogeneity). The arrangement shown is illustrative and otherarrangements are suitable. Techniques for patterning phosphors aredisclosed in U.S. application Ser. No. 14/135,098, filed on Dec. 19,2013, which is incorporated by reference in its entirety.

In some embodiments of the invention, the LEDs from Groups 1 and 2 areoptically isolated from each other. For instance, an optical barrier(which may be a reflective element, or an optical element such as alens) is positioned between the LEDs from Groups 1 and 2. Thus, theradiation emitted by Group 1 LEDs does not significantly impinge on theGroup 2 LEDs, and vice-versa. For instance, in some embodiments, lessthan 10% (or less than 1%) of the radiation emitted by Group 1 LEDsimpinges on Group 2 LEDs, and vice-versa. This may be desirable in someembodiments where cross-pumping between the LEDs is not desirable. Forinstance, in some embodiments Group 1 LEDs emit an SPD with little bluelight having relatively low circadian stimulation and Group 2 emits anSPD with more blue light having relatively high circadian stimulation;in such embodiments it may be undesirable that radiation from Group 1LEDs optically excite Group 2 LEDs, as this may result in luminescencefrom Group 2 LEDs even though the Group 2 LEDs are not electricallyinjected (thus leading to an unwanted presence of blue light in theemitted SPD). Likewise, the optical design of the system, including itsoptics, may be designed so that there is little optical cross-excitationbetween Group 1 and Group 2 LEDs. One skilled in the art may achievethis by designing the optical system while taking into accountreflection and scattering of light emitted by Groups 1 and 2.

More generally, in embodiments having more than one Group of LEDsemitting distinct SPDs, it may be desirable to design the system so thatoptical cross-excitation between Groups is minimized.

Another embodiment of the invention includes circadian-friendlydirectional light sources.

In some embodiments of the invention, directional light sources areimplemented with a multiple-optic approach. A directional optic isattached to each LED emitter. The LED emitter may be small (it may havea characteristic lateral dimension of less than 2 mm, less than 1 mm,less than 500 um, less than 100 um). A directional micro-optic isconfigured to capture the light from each LED emitter. The LEDs may beseparated optically by an optical blocking element. In some embodimentsthe directional optics are configured above the LED emitters; in others,the directional optics are configured around the LED emitters, thuscapturing and directing lateral light emitted by the sides of the LEDemitters. The directional optics may produce directional light beams,with the beam from all emitters blending in the far-field pattern. Insome embodiments, each emitter consists of a pump LED andwavelength-converting materials. In some embodiments, Group 1 LEDs emitan SPD with little blue light having relatively low circadianstimulation and Group 2 emits an SPD with more blue light havingrelatively high circadian stimulation. Thus, by separately driving theLEDs of Groups 1 and 2, the emitted light can switch from a lowexcitation circadian-friendly mode to a circadian-entraining mode. Insome embodiments, the pump LEDs of at least one Group are violetemitters. In some embodiments, the pump LEDs of the circadian-entrainingGroup are blue LEDs. Some embodiments comprise more than two Groups; forinstance they may contain a direct green or a direct red LED. In variousembodiments, the layout of the LEDs and the optics are configured toobtain a desired beam, for instance a beam with homogeneouschromaticity.

FIG. 9A presents a selection of lamp shapes corresponding toknown-in-the-art standards. The aforementioned lamps are merely selectedembodiments of lamps that conform to fit with any one or more of a setof mechanical and electrical standards. Table 1 gives standards (see“Designation”) and corresponding characteristics.

TABLE 1 Base Diameter IEC 60061-1 Desig- (Crest of Standard nationthread) Name Sheet E05 05 mm Lilliput Edison Screw (LES) 7004-25 E10 10mm Miniature Edison Screw (MES) 7004-22 E11 11 mm Mini-Candelabra EdisonScrew (7004-06-1) (mini-can) E12 12 mm Candelabra Edison Screw (CES)7004-28 E14 14 mm Small Edison Screw (SES) 7004-23 E17 17 mmIntermediate Edison Screw (IES) 7004-26 E26 26 mm [Medium] (one-inch)Edison 7004-21A-2 Screw (ES or MES) E27 27 mm [Medium] Edison Screw (ES)7004-21 E29 29 mm [Addendum] Edison Screw (ES) E39 39 mm Single-contact(Mogul) Giant 7004-24-A1 Edison Screw (GES) E40 40 mm (Mogul) GiantEdison Screw 7004-24 (GES)

Additionally, the base member of a lamp can be of any form factorconfigured to support electrical connections, which electricalconnections can conform to any of a set of types or standards. Forexample Table 2 gives standards (see “Type”) and correspondingcharacteristics, including mechanical spacing between a first pin (e.g.,a power pin) and a second pin (e.g., a ground pin).

TABLE 2 Pin center Pin Type Standard to center Diameter Usage G4 IEC60061-1 4.0 mm 0.65-0.75 mm MR11 and other small halogens of (7004-72)5/10/20 watt and 6/12 volt GU4 IEC 60061-1 4.0 mm 0.95-1.05 mm(7004-108) GY4 IEC 60061-1 4.0 mm 0.65-0.75 mm (7004-72A) GZ4 IEC60061-1 4.0 mm 0.95-1.05 mm (7004-64) G5 IEC 60061-1 5 mm T4 and T5fluorescent tubes (7004-52-5) G5.3 IEC 60061-1 5.33 mm 1.47-1.65 mm(7004-73) G5.3-4.8 IEC 60061-1 (7004-126-1) GU5.3 IEC 60061-1 5.33 mm1.45-1.6 mm (7004-109) GX5.3 IEC 60061-1 5.33 mm 1.45-1.6 mm MR16 andother small halogens of (7004-73A) 20/35/50 watt and 12/24 volt GY5.3IEC 60061-1 5.33 mm (7004-73B) G6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm(7004-59) GX6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm (7004-59) GY6.35 IEC60061-1 6.35 mm 1.2-1.3 mm Halogen 100 W 120 V (7004-59) GZ6.35 IEC60061-1 6.35 mm 0.95-1.05 mm (7004-59A) G8 8.0 mm Halogen 100 W 120 VGY8.6 8.6 mm Halogen 100 W 120 V G9 IEC 60061-1 9.0 mm Halogen 120 V(US)/230 V (EU) (7004-129) G9.5 9.5 mm 3.10-3.25 mm Common for theatreuse, several variants GU10 10 mm Twist-lock 120/230-volt MR16 halogenlighting of 35/50 watt, since mid-2000s G12 12.0 mm 2.35 mm Used intheatre and single-end metal halide lamps G13 12.7 mm T8 and T12fluorescent tubes G23 23 mm 2 mm GU24 24 mm Twist-lock forself-ballasted compact fluorescents, since 2000s G38 38 mm Mostly usedfor high-wattage theatre lamps GX53 53 mm Twist-lock for puck-shapedunder- cabinet compact fluorescents, since 2000s

The list above is representative and should not be taken to include allthe standards or form factors that may be utilized within embodimentsdescribed herein.

FIG. 9B through FIG. 9I present selections of troffers corresponding tovarious shapes (e.g., substantially square, substantially rectangular)and installation configurations (e.g., recessed, flush mounted, hanging,etc.). Combinations of the foregoing multi-track driver control system(see FIG. 7), and strings of LEDs in an intermixed physical arrangement(see FIG. 8) can be used with the exemplary troffers and/or with anysorts of general illumination fixtures.

Other luminaires such as suspended luminaires may emit light upwardrather than downward, or may emit light in both directions.

FIG. 10A through FIG. 10I depict embodiments of the present disclosurein the form of lamp applications. In these lamp applications, one ormore light emitting diodes are used in lamps and fixtures. Such lampsand fixtures include replacement and/or retro-fit directional lightingfixtures.

In some embodiments, aspects of the present disclosure can be used in anassembly. As shown in FIG. 10A, the assembly comprises:

-   -   a screw cap 1028    -   a driver housing 1026    -   a driver board 1024    -   a heatsink 1022    -   a metal-core printed circuit board 1020    -   an LED light source 1018    -   a dust shield 1016    -   a lens 1014    -   a reflector disc 1012    -   a magnet 1010    -   a magnet cap 1008    -   a trim ring 1006    -   a first accessory 1004    -   a second accessory 1002

The components of assembly 10A00 may be described in substantial detail.Some components are ‘active components’ and some are ‘passive’components, and can be variously-described based on the particularcomponent's impact to the overall design, and/or impact(s) to theobjective optimization function. A component can be described using aCAD/CAM drawing or model, and the CAD/CAM model can be analyzed so as toextract figures of merit as may pertain to e particular component'simpact to the overall design, and/or impact(s) to the objectiveoptimization function. Strictly as one example, a CAD/CAM model of atrim ring is provided in a model corresponding to the drawing of FIG.10A2.

The components of the assembly 10B100 and assembly 10B200 can be fittedtogether to form a lamp. FIG. 10B1 depicts a perspective view 1030 andFIG. 10B2 depicts a top view 1032 of such a lamp. As shown in FIG. 10B1and FIG. 10B2, the lamp 10B100 and 10B200 comports to a form factorknown as PAR30L. The PAR30L form factor is further depicted by theprincipal views (e.g., left 1040, right 1036, back 1034, front 1038 andtop 1042) given in array 10C00 of FIG. 10C.

The components of the assembly 10D100 and assembly 10D200 can be fittedtogether to form a lamp. FIG. 10D1 depicts a perspective view 1044 andFIG. 10D2 depicts a top view 1046 of such a lamp. As shown in FIG. 10D1and in FIG. 10D2, the lamp 10D100 and 10D200 comports to a form factorknown as PAR30S. The PAR30S form factor is further depicted by theprincipal views (e.g., left 1054, right 1050, back 1048, front 1052 andtop 1056) given in array 10E00 of FIG. 10E.

The components of the assembly 10A00 can be fitted together to form alamp. FIG. 10F1 depicts a perspective view 1058 and FIG. 10F2 depicts atop view 1060 of such a lamp. As shown in FIG. 10F1 and FIG. 10F2, thelamp 10F100 and 10F200 comports to a form factor known as PAR38. ThePAR38 form factor is further depicted by the principal views (e.g., left1068, right 1064, back 1062, front 1066 and top 1070) given in array10G00 of FIG. 10G.

The components of the assembly 10A00 can be fitted together to form alamp. FIG. 10H1 depicts a perspective view 1072 and FIG. 10H2 depicts atop view 1074 of such a lamp. As shown in FIG. 10H1 and FIG. 10H2, thelamp 10H100 and 10H200 comports to a form factor known as PAR111. ThePAR111 form factor is further depicted by the principal views (e.g.,left 1082, right 1078, back 1076, front 1080 and top 1084) given inarray 10I00 of FIG. 10I.

In addition to uses of the aforementioned lamps and lamp shapes, filtersor so-called ‘circadian phosphors’ can be employed.

Various implementations can be considered to alter an SPD's impact onthe circadian system. As discussed above, it is possible to use amultiple-channel system including violet-pump and blue-pump LEDs and tobalance the contribution of both channels. Besides, it is possible tophysically block a given spectral range (such as the blue, cyan orviolet region)—for instance by using absorbing or reflecting filterswhich may be fixed or moving. Filters offer the advantage that asubstantial amount of light (or even all the light) can be blocked in agiven spectral range, which may be of importance. For instance, it maybe desirable to block nearly all the light in the blue-cyan range (or ina more specific range) to obtain a very low circadian stimulation—thisis because standard spectra (such as a dimmed filament lamp) still havea fair amount of circadian stimulation. Such filters may for instance bedichroic reflective filters or absorbing filters including dye filtersin a matrix (glass, plastic or other)

The specific design of a dichroic filter will be exemplified further inthis document.

Another option, however, is to use a light-converting material in thesystem with a carefully chosen absorption range. For instance, one mayinclude a phosphor which absorbs blue light and down-converts it togreen or red light. This approach may be desirable because it enablesone to remove a substantial amount of light in the absorption range likea blocking approach would, but with higher system efficiency since theradiation is converted to another wavelength rather than merely beingblocked. For simplicity, this phosphor is called the ‘circadianphosphor’, since its absorption has an impact on the circadian action ofthe light source.

FIG. 11A and FIG. 11B contrasts the two approaches. FIG. 11A shows theinitial SPD of a white LED source 1101 and the filtered SPD 1102 afterblue light is blocked by a filter. The filtered SPD 1102 can be used inmany embodiments, as it has a low amount of blue light, which can reducedisruption of the circadian system; furthermore the width and generalshape of the filter may be designed to control this effect. However,filtering induces a penalty in efficiency because the filtered light islost.

FIG. 11B shows the initial SPD of a white LED source 1103 and theconverted SPD 1104 after blue light is absorbed by a “circadianphosphor” and converted to yellow light 1105. In this case, the samedesirable effect on the circadian system is obtained, but the impact onefficiency is lessened thanks to the conversion of blue light. Hereagain, various aspects of the approach can be controlled through design,such as the position and amplitude of the absorption dip, whichabsorption dip can be controlled through the choice and amount ofphosphor, and the position and amplitude of the luminescence. Forinstance, the absorption may be chosen to substantially block blue lightbut to allow some violet light transmission.

The circadian phosphor may be static, in which case the emitted SPD doesnot vary, or it may be on a moving part in order to control the SPDdynamically. The moving part may be a plate containing the phosphor,which can be moved mechanically in and out of the path of light emissionof the system.

In FIG. 11A and FIG. 11B, the embodiments are designed to remove lightin the range 440 nm to 460 nm. By choosing other filters or otherphosphors this range can be tuned—for instance the range 450 nm to 480nm, or another range, can be targeted and the spectral power in therange reduced. In some embodiments, a specific circadian action spectrumis assumed and the SPD is designed to have a low amount of light in therange where the action spectrum is high.

In yet another embodiment, the circadian phosphor shows a saturationbehavior: it absorbs light at low flux, but absorption saturates at highflux. Such an approach is illustrated in FIG. 12 through FIG. 14.

FIG. 12 shows various spectra. Spectrum 1201 is an emission spectrum ofa white LED source with a CCT of 3000K and a CRI of about 90. Thisspectrum may be obtained by combining a violet-pump LED and severalphosphors (e.g., a green phosphor, a red phosphor and possibly a bluephosphor). Curve 1202 is the absorption spectrum of a saturable redcircadian phosphor and curve 1203 is the corresponding luminescencespectrum. Spectrum 1202 and spectrum 1203 can be obtained, for instance,with Mn-doped phosphors such as K₂[TiF₆]:Mn⁴⁺.

FIG. 13 shows a possible way to combine such a white LED source and sucha saturable phosphor. In FIG. 13, the saturable circadian phosphor 1302is placed above the LED source 1301 so that the white light emitted bythe device 1303 can be absorbed by the circadian phosphor. Various otherconfigurations are also possible—for instance, the circadian phosphormay be mixed with the phosphors of the white LED or may be in a remoteconfiguration.

FIG. 14A and FIG. 14B show the resulting spectral and colorimetricproperties of the system shown in FIG. 13. FIG. 14A shows the spectrumemitted by the system at various LED drive currents. At low drivecurrent the saturable phosphor is not saturated and absorbs most of thelight in its absorption range (e.g., blue-cyan light), resulting inpectrum 1401. At higher drive current the phosphor absorption ispartially saturated and part of the blue-cyan light is transmitted,resulting in spectrum 1402. At even higher drive current the phosphorabsorption is fully saturated, and the original spectrum of the whiteLED 1403 is emitted with very little perturbation from the circadianphosphor. FIG. 14B shows the corresponding chromaticity in (x, y) spacefor each drive current. At low drive current the CCT is about 2000K1405, at higher drive current it is about 2500K 1406 and at the highestdrive current it is about 3000K 1407. In all cases, the chromaticity isclose to the Planckian locus 1404.

The embodiments of FIG. 12 through FIG. 14 achieve several desirableproperties. At high drive current (e.g., see curve 1402), theembodiments behave like a conventional halogen retrofit with a high CRI(e.g., the circadian stimulation is 128% relative to standard illuminantA). As the current is reduced (e.g., see curves 1403 and 1401), thechromaticity shifts toward lower CCT (from 1407 to 1406 to 1405) thusemulating the behavior of a dimmed halogen or incandescent lamp. Inaddition, the spectrum is modified so that circadian stimulationdecreases; at the lowest drive condition there is very little radiationin the range 440 nm to 490 nm (e.g., see curve 1401) and therefore verylow stimulation of the circadian system (the circadian stimulation isonly 8% relative to standard illuminant A).

As in other embodiments, the properties of the SPDs shown in FIG. 14Acan be characterized by their relative fraction of power Fv in the range400 nm to 440 nm and the fraction of power Fc in the range 440 nm to 500nm. For SPD 1401, Fv=0.06 and Fc=0.01; for SPD 1402, Fv=0.08 andFc=0.12. The value of Fc is especially low for SPD 1401, which can beassociated with a very low circadian stimulation. This is in contrast totypical LED sources where a substantial fraction of power is in therange 440 nm to 500 nm (even for low-CCT sources with a CCT below2700K).

While sources of varying CCT are known in the art and can be useful tomodulate circadian stimulation, this embodiment has superior properties.The circadian stimulation is extremely low at low drive conditions: itis indeed lower than what is achieved with conventional LED sources,which employ a blue pump LED, or even by dimming of a conventionalincandescent/halogen lamp. For example, a dimmed filament lamp emittinga blackbody spectrum with a CCT of 2000K still has a circadianstimulation of about 54% relative to illuminant A. Furthermore thepresent embodiment is ‘passive’ in that it doesn't require multiplechannel drivers to modulate the spectrum. Therefore, such an embodimentmay be integrated to a retrofit lamp or more generally a lighting systemin absence of any advanced control circuits. In some such cases standarddimming switches provides the needed control.

In this embodiment, the presence of a violet pump is of importance sincethe violet light enables the chromaticity to be near-Planckian at lowdrive current, even in the absence of blue-cyan light.

Various aspects of this embodiment can be advantageously controlled. Forinstance, the optical properties of the pump LED can be varied, and theselection of phosphors can be varied, and the relative loading ofphosphors can be varied to accomplish an optimization objective. Theoptimization criteria may include the CRI of the source at variousdimming levels, its chromaticity and various dimming level, and metricsrelated to its circadian impact at various dimming levels. Strictly asone example, optimization criteria may include aspects of an integratedcircadian action spectrum. The loading of the circadian phosphor can bechosen so that its saturation occurs at a desired drive, such as, forinstance, 10% dimming. In other embodiments, more than one circadianphosphor is used.

In other embodiment, the white LED is obtained by multiple LED chips,such as uses of a violet LED, a green LED and a red LED rather than aphosphor-converted LED. In other embodiments, the chromaticity of thesource does not follow the Planckian locus—it may for instance be belowthe Planckian locus, which is sometimes associated with a preferredperception as already discussed.

Embodiments may be integrated to various systems. This includes lightingsystems (e.g., lamps, troffers and others) and non-lighting systems(e.g., display applications).

FIG. 15A1 through FIG. 15I depict embodiments of the present disclosureas can be applied toward lighting applications. In these embodiments, asshown in FIGS. 15A1-15A3, one or more light-emitting diodes 15A10, astaught by this disclosure, can be mounted on a submount or package toprovide an electrical interconnection. As shown in FIGS. 15B1-15B3 asubmount or package can be a ceramic, oxide, nitride, semiconductor,metal, or combination thereof that includes an electricalinterconnection capability 15A20 for the various LEDs. The submount orpackage can be mounted to a heatsink member 15B50 via a thermalinterface. The LEDs can be configured to produce a desired emissionspectrum, either by mixing primary emissions from various LEDs, or byhaving the LEDs photo-excite wavelength down-conversion materials suchas phosphors, semiconductors, or semiconductor nanoparticles (“quantumdots”), or a combination of any of the foregoing.

The total light emitting surface (LES) of the LEDs and anydown-conversion materials can form a light source 15A30. One or morelight sources can be interconnected into an array 15B20, which in turnis in electrical contact with connectors 15B10 and brought into anassembly 15B30. One or more lens elements 15B40 can be optically coupledto the light source. The lens design and properties can be selected sothat the desired directional beam pattern for a lighting product isachieved for a given LES. The directional lighting product may be an LEDmodule, a retrofit lamp 15B70, or a lighting fixture 15C30. In the caseof a retrofit lamp, an electronic driver can be provided with asurrounding member 15B60, the driver to condition electrical power froman external source to render it suitable for the LED light source. Thedriver can be integrated into the retrofit lamp. In the case of afixture, an electronic driver is provided which conditions electricalpower from an external source to make it suitable for the LED lightsource, with the driver either integrated into the fixture or providedexternally to the fixture. In the case of a module, an electronic drivercan be provided to condition electrical power from an external source torender it suitable for the LED light source, with the driver eitherintegrated into the module or provided externally to the module.Examples of suitable external power sources include mains AC (e.g., 120Vrms AC or 240 Vrms AC), low-voltage AC (e.g., 12 VAC), and low-voltageDC (e.g., 12 VDC). In the case of retrofit lamps, the entire lightingproduct may be designed to fit standard form factors (e.g., ANSI formfactors). Examples of retrofit lamp products include LED-based MR16,PAR16, PAR20, PAR30, PAR38, BR30, A19 and various other lamp types.Examples of fixtures include replacements for halogen-based and ceramicmetal halide-based directional lighting fixtures.

In some embodiments, the present disclosure can be applied tonon-directional lighting applications. In these embodiments, one or morelight-emitting diodes (LEDs), as taught by the disclosure, can bemounted on a submount or package to provide an electricalinterconnection. The submount or package can be, for example, a ceramic,oxide, nitride, semiconductor, metal, or combination of any of theforegoing that includes electrical interconnection capability for thevarious LEDs. The submount or package can be mounted to a heatsinkmember via a thermal interface. The LEDs can be configured to produce adesired emission spectrum, either by mixing primary emissions fromvarious LEDs, or by having the LEDs photo-excite wavelengthdown-conversion materials such as phosphors, semiconductors, orsemiconductor nanoparticles (“quantum dots”), or a combination thereof.The LEDs can be distributed to provide a desired shape of the lightsource. For example, one common shape is a linear light source forreplacement of conventional fluorescent linear tube lamps. One or moreoptical elements can be coupled to the LEDs to provide a desirednon-directional light distribution. The non-directional lighting productmay be an LED module, a retrofit lamp, or a lighting fixture. In thecase of a retrofit lamp, an electronic driver can be provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver integrated into the retrofitlamp. In the case of a fixture, an electronic driver is provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver either integrated into thefixture or provided externally to the fixture. In the case of a module,an electronic driver can be provided to condition electrical power froman external source to render it suitable for the LED light source, withthe driver either integrated into the module or provided externally tothe module. Examples of external power sources include mains AC (e.g.,120 Vrms AC or 240 Vrms AC), low-voltage AC (e.g., 12 VAC), andlow-voltage DC (e.g., 12 VDC). In the case of retrofit lamps, the entirelighting product may be designed to fit standard form factors (e.g.,ANSI form factors). Examples of non-directional lighting products areshown in FIG. 15C1, FIG. 15C2, and FIG. 15C3. Such a lighting fixturecan include replacements for fluorescent-based troffer luminaires 15C30.In this embodiment, LEDs are mechanically secured into a package 15C10,and multiple packages are arranged into a suitable shape such as lineararray 15C20.

Some embodiments of the present disclosure can be applied tobacklighting for flat panel display applications. In these embodiments,one or more light-emitting diodes (LEDs), as taught by this disclosure,can be mounted on a submount or package to provide an electricalinterconnection. The submount or package can be a ceramic, oxide,nitride, semiconductor, metal, or combination of any of the foregoingthat include electrical interconnection capability for the various LEDs.The submount or package can be mounted to a heatsink member via athermal interface. The LEDs can be configured to produce a desiredemission spectrum, either by mixing primary emissions from various LEDs,or by having the LEDs photo-excite wavelength down-conversion materialssuch as phosphors, semiconductors, or semiconductor nanoparticles(“quantum dots”), or a combination of any of the foregoing. The LEDs canbe distributed to provide a desired shape of the light source. Onecommon shape is a linear light source. The light source can be opticallycoupled to a lightguide for the backlight. This can be achieved bycoupling at the edge of the lightguide (edge-lit), or by coupling lightfrom behind the lightguide (direct-lit). The lightguide distributeslight uniformly toward a controllable display such as a liquid crystaldisplay (LCD) panel. The display converts the LED light into desiredimages based on electrical control of light transmission and its color.One way to control the color is by use of filters (e.g., color filtersubstrate 15D40). Alternatively, multiple LEDs may be used and driven inpulsed mode to sequence the desired primary emission colors (e.g., usinga red LED 15D30, a green LED 15D10, and a blue LED 15D20). Optionalbrightness-enhancing films may be included in the backlight “stack”. Thebrightness-enhancing films narrow the flat panel display emission toincrease brightness at the expense of the observer-viewing angle. Anelectronic driver can be provided to condition electrical power from anexternal source to render it suitable for the LED light source forbacklighting, including any color sequencing or brightness variation perLED location (e.g., one-dimensional or two-dimensional dimming).Examples of external power sources include mains AC (e.g., 120 Vrms ACor 240 Vrms AC), low-voltage AC (e.g., 12 VAC), and low-voltage DC(e.g., 12 VDC). Examples of backlighting products are shown in FIG. 15Dand FIG. 15E.

Some embodiments of the present disclosure can be applied to automotiveforward lighting applications, as shown in FIGS. 15F1-15F (e.g., see theexample of an automotive forward lighting product 15F30). In theseembodiments, one or more light-emitting diodes (LEDs) can be mounted ona submount or on a rigid or semi-rigid package 15F10 to provide anelectrical interconnection. The submount or package can be a ceramic,oxide, nitride, semiconductor, metal, or combination thereof, thatinclude electrical interconnection capability for the various LEDs. Thesubmount or package can be mounted to a heatsink member via a thermalinterface. The LEDs can be configured to produce a desired emissionspectrum, either by mixing primary emission from various LEDs, or byhaving the LEDs photo-excite wavelength down-conversion materials suchas phosphors, semiconductors, or semiconductor nanoparticles (“quantumdots”), or a combination of any of the foregoing. The total lightemitting surface (LES) of the LEDs and any down-conversion materialsform a light source. One or more lens elements 15F20 can be opticallycoupled to the light source. The lens design and properties can beselected to produce a desired directional beam pattern for an automotiveforward lighting application for a given LED. An electronic driver canbe provided to condition electrical power from an external source torender it suitable for the LED light source. Power sources forautomotive applications include low-voltage DC (e.g., 12 VDC). An LEDlight source may perform a high-beam function, a low-beam function, aside-beam function, or any combination thereof.

Certain embodiments of the present disclosure can be applied to digitalimaging applications such as illumination for mobile phone and digitalstill cameras (e.g., see FIGS. 15G1-15G4). In these embodiments, one ormore light-emitting diodes (LEDs), as taught by the disclosure, can bemounted on a submount or package 15G10 to provide an electricalinterconnection. The submount or package can be, for example, a ceramic,oxide, nitride, semiconductor, metal, or combination of any of theforegoing that include electrical interconnection capability for thevarious LEDs. The submount or package can be mounted to a circuit boardmember and fitted with or into a mounting package 15G20. The LEDs can beconfigured to produce a desired emission spectrum, either by mixingprimary emission from various LEDs, or by having the LEDs photo-excitewavelength down-conversion materials such as phosphors, semiconductors,or semiconductor nanoparticles (“quantum dots”), or a combinationthereof. The total light emitting surface (LES) of the LEDs and anydown-conversion materials form a light source. One or more lens elementscan be optically coupled to the light source. The lens design andproperties can be selected so that the desired directional beam patternfor an imaging application is achieved for a given LES. An electronicdriver can be provided to condition electrical power from an externalsource to render it suitable for the LED light source. Examples ofsuitable external power sources for imaging applications includelow-voltage DC (e.g., 5 VDC). An LED light source may perform alow-intensity function 15G30, a high-intensity function 15G40, or anycombination thereof.

Some embodiments of the present disclosure can be applied to mobileterminal applications. FIG. 15H is a diagram illustrating a mobileterminal (see smart phone architecture 15H00). As shown, the smart phone15H06 includes a housing, display screen, and interface device, whichmay include a button, microphone, and/or touch screen. In certainembodiments, a phone has a high resolution camera device, which can beused in various modes. An example of a smart phone can be an iPhone fromApple Inc. of Cupertino, Calif. Alternatively, a smart phone can be aGalaxy from Samsung, or others.

In an example, the smart phone may include one or more of the followingfeatures (which are found in an iPhone 4 from Apple Inc., although therecan be variations), see www.apple.com:

-   -   GSM model: UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz); GSM/EDGE        (850, 900, 1800, 1900 MHz)    -   CDMA model: CDMA EV-DO Rev. A (800, 1900 MHz)    -   802.11b/g/n Wi-Fi (802.11n 2.4 GHz only)    -   Bluetooth 2.1+EDR wireless technology    -   Assisted GPS    -   Digital compass    -   Wi-Fi    -   Cellular    -   Retina display    -   3.5-inch (diagonal) widescreen multi-touch display    -   800:1 contrast ratio (typical)    -   500 cd/m2 max brightness (typical)    -   Fingerprint-resistant oleophobic coating on front and back    -   Support for display of multiple languages and characters        simultaneously    -   5-megapixel iSight camera    -   Video recording, HD (720p) up to 30 frames per second with audio    -   VGA-quality photos and video at up to 30 frames per second with        the front camera    -   Tap to focus video or still images    -   LED flash    -   Photo and video geotagging    -   Built-in rechargeable lithium-ion battery    -   Charging via USB to computer system or power adapter    -   Talk time: Up to 20 hours on 3G, up to 14 hours on 2G (GSM)    -   Standby time: Up to 300 hours    -   Internet use: Up to 6 hours on 3G, up to 10 hours on Wi-Fi    -   Video playback: Up to 10 hours    -   Audio playback: Up to 40 hours    -   Frequency response: 20 Hz to 22,000 Hz    -   Audio formats supported: AAC (8 to 320 Kbps), protected AAC        (from iTunes Store), HE-AAC, MP3 (8 to 320 Kbps), MP3 VBR,        audible (formats 2, 3, 4, audible enhanced audio, AAX, and        AAX+), Apple lossless, AIFF, and WAV    -   User-configurable maximum volume limit    -   Video out support with Apple digital AV adapter or Apple VGA        adapter; 576p and 480p with Apple component AV cable; 576i and        480i with Apple composite AV cable (cables sold separately)    -   Video formats supported: H.264 video up to1080p, 30 frames per        second, main profile Level 3.1 with AAC-LC audio up to 160 Kbps,        48 kHz, stereo audio in .m4v, .mp4, and .mov file formats;        MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per        second, simple profile with AAC-LC audio up to 160 Kbps per        channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file        formats; motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 1020        pixels, 30 frames per second, audio in ulaw, PCM stereo audio in        .avi file format    -   Three-axis gyro    -   Accelerometer    -   Proximity sensor    -   Ambient light sensor, etc.

Embodiments of the present disclosure may be used with other electronicdevices. Examples of suitable electronic devices include a portableelectronic device such as a media player, a cellular phone, a personaldata organizer, or the like. In such embodiments, a portable electronicdevice may include a combination of the functionalities of such devices.In addition, an electronic device may allow a user to connect to andcommunicate through the Internet or through other networks such as localor wide area networks. For example, a portable electronic device mayallow a user to access the internet and to communicate using e-mail,text messaging, instant messaging, or using other forms of electroniccommunication. By way of example, the electronic device may be similarto an iPod having a display screen or an iPhone available from AppleInc.

In certain embodiments, a device may be powered by one or morerechargeable and/or replaceable batteries. Such embodiments may behighly portable, allowing a user to carry the electronic device whiletraveling, working, exercising, and so forth. In this manner, anddepending on the functionalities provided by the electronic device, auser may listen to music, play games or video, record video or takepictures, place and receive telephone calls, communicate with others,control other devices (e.g., via remote control and/or Bluetoothfunctionality), and so forth while moving freely with the device. Inaddition, the device may be sized such that it fits relatively easilyinto a pocket or the hand of the user. While certain embodiments of thepresent disclosure are described with respect to portable electronicdevices, it should be noted that the presently disclosed techniques maybe applicable to a wide array of other, less portable, electronicdevices and systems that are configured to render graphical data such asa desktop computer.

As shown, FIG. 15H includes a system diagram with a smart phone thatincludes an LED according to an embodiment of the present disclosure.The smart phone 15H06 is configured to communicate with a server 15H02in electronic communication with any forms of handheld electronicdevices. Illustrative examples of such handheld electronic devices caninclude functional components such as a processor 15H08, memory 15H10,graphics accelerator 15H12, accelerometer 15H14, communicationsinterface 15H11 (possibly including an antenna 15H16), compass 15H18,GPS chip 15H20, display screen 15H22, and an input device 15H24. Eachdevice is not limited to the illustrated components. The components maybe hardware, software or a combination of both.

In some examples, instructions can be input to the handheld electronicdevice through an input device 15H24 that instructs the processor 15H08to execute functions in an electronic imaging application. One potentialinstruction can be to generate an abstract of a captured image of aportion of a human user. In that case the processor 15H08 instructs thecommunications interface 15H11 to communicate with the server 15H02(e.g., possibly through or using a cloud 15H04) and transfer data (e.g.,image data). The data is transferred by the communications interface15H11 and either processed by the processor 15H08 immediately afterimage capture or stored in memory 15H10 for later use, or both. Theprocessor 15H08 also receives information regarding the display screen'sattributes, and can calculate the orientation of the device, e.g., usinginformation from an accelerometer 15H14 and/or other external data suchas compass headings from a compass 15H18, or GPS location from a GPSchip 15H20, and the processor then uses the information to determine anorientation in which to display the image depending upon the example.

The captured image can be rendered by the processor 15H08, by a graphicsaccelerator 15H12, or by a combination of the two. In some embodiments,the processor can be the graphics accelerator 15H12. The image can firstbe stored in memory 15H10 or, if available, the memory can be directlyassociated with the graphics accelerator 15H12. The methods describedherein can be implemented by the processor 15H08, the graphicsaccelerator 15H12, or a combination of the two to create the image andrelated abstract. An image or abstract can be displayed on the displayscreen 15H22.

FIG. 15I depicts an interconnection of components in an electronicdevice 15100. Examples of electronic devices include an enclosure orhousing, a display, user input structures, and input/output connectorsin addition to the aforementioned interconnection of components. Theenclosure may be formed from plastic, metal, composite materials, orother suitable materials, or any combination thereof. The enclosure mayprotect the interior components of the electronic device from physicaldamage, and may also shield the interior components from electromagneticinterference (EMI).

The display may be a liquid crystal display (LCD), a light emittingdiode (LED) based display, an organic light emitting diode (OLED) baseddisplay, or some other suitable display. In accordance with certainembodiments of the present disclosure, the display may display a userinterface and various other images such as logos, avatars, photos, albumart, and the like. Additionally, in certain embodiments, a display mayinclude a touch screen through which a user may interact with the userinterface. The display may also include various functions and/or systemindicators to provide feedback to a user such as power status, callstatus, memory status, or the like. These indicators may be incorporatedinto the user interface displayed on the display.

In certain embodiments, one or more of the user input structures can beconfigured to control the device such as by controlling a mode ofoperation, an output level, an output type, etc. For instance, the userinput structures may include a button to turn the device on or off.Further, the user input structures may allow a user to interact with theuser interface on the display. Embodiments of the portable electronicdevice may include any number of user input structures includingbuttons, switches, a control pad, a scroll wheel, or any other suitableinput structures. The user input structures may work with the userinterface displayed on the device to control functions of the deviceand/or any interfaces or devices connected to or used by the device. Forexample, the user input structures may allow a user to navigate adisplayed user interface or to return such a displayed user interface toa default or home screen.

Certain device may also include various input and output ports to allowconnection of additional devices. For example, a port may be a headphonejack that provides for the connection of headphones. Additionally, aport may have both input and output capabilities to provide for theconnection of a headset (e.g., a headphone and microphone combination).Embodiments of the present disclosure may include any number of inputand/or output ports such as headphone and headset jacks, universalserial bus (USB) ports, IEEE-1394 ports, and AC and/or DC powerconnectors. Further, a device may use the input and output ports toconnect to and send or receive data with any other device such as otherportable electronic devices, personal computers, printers, or the like.For example, in one embodiment, the device may connect to a personalcomputer via an IEEE-1394 connection to send and receive data files suchas media files.

The depiction of an electronic device 15I00 encompasses a smart phonesystem diagram according to an embodiment of the present disclosure. Thedepiction of an electronic device 15I00 illustrates computer hardware,software, and firmware that can be used to implement the disclosuresabove. The shown system includes a processor 15I26, which isrepresentative of any number of physically and/or logically distinctresources capable of executing software, firmware, and hardwareconfigured to perform identified computations. A processor 15I26communicates with a chipset 15I28 that can control input to and outputfrom processor 15I26. In this example, chipset 15I28 outputs informationto display screen 15I42 and can read and write information tonon-volatile storage 15I44, which can include magnetic media and solidstate media, and/or other non-transitory media, for example. Chipset15I28 can also read data from and write data to RAM 15I46. A bridge15I32 for interfacing with a variety of user interface components can beprovided for interfacing with chipset 15I28. Such user interfacecomponents can include a keyboard 15I34, a microphone 15I36,touch-detection-and-processing circuitry 15I38, a pointing device 15I40such as a mouse, and so on. In general, nputs to the system can comefrom any of a variety of machine-generated and/or human-generatedsources.

Chipset 15I28 also can interface with one or more data networkinterfaces 15I30 that can have different physical interfaces. Such datanetwork interfaces 15I30 can include interfaces for wired and wirelesslocal area networks, for broadband wireless networks, as well aspersonal area networks. Some applications of the methods for generating,displaying and using the GUI disclosed herein can include receiving dataover a physical interface 15I31 or be generated by the machine itself bya processor 15I26 analyzing data stored in non-volatile storage 15I44and/or in memory or RAM 15I46. Further, the machine can receive inputsfrom a user via devices such as a keyboard 15I34, microphone 15I36,touch-detection-and-processing circuitry 15I38, and pointing device15I40 and execute appropriate functions such as browsing functions byinterpreting these inputs using processor 15I26.

Filtering Based on Clinical Measurements

Assessing the impact of a light-emitting system on the circadian cyclemay be performed in a variety of ways, including using medical orclinical trials. In such trials, various physiological signals relatedto the circadian cycle may be monitored for subjects exposed to thelight-emitting system. For instance, it is possible to measure themelatonin suppression in the saliva or blood of the subjects. Otherphysiological signals, including various hormones, may be measured fromsaliva or blood samples or in other tests. Such protocols are known tothose skilled in the art and are discussed in scientific publications. Aspecific physiological response (such as the level of a specifichormone) may be targeted in such tests, especially for responses knownto correlate to a specific medical condition and/or a condition known orbelieved to be associated with the spectral content of light.

For instance, Brainard discloses a protocol for measuring the melatoninsuppression under light exposure. Some steps of the protocol are asfollows.

-   -   Subjects with normal vision are selected.    -   At midnight, the subjects enter a dimly lit room, their pupils        are dilated and they wait for a period of 2 hrs.    -   A blood sample if taken.    -   The subjects are exposed to the test light for 90 min, and a        second blood sample is taken.    -   The melatonin content in the blood samples is determined, and        the relative decrease in melatonin compared to that in a control        experiment (e.g., no light exposure).

Other testing protocols can be found in various publications such as,for example, in West et al.; in “Blue light from light-emitting diodeselicits a dose-dependent suppression of melatonin in humans” J. Appl.Physiol.110, 619-626 (2011)).

It can be appreciated that the disclosed techniques can be applied tolighting or display systems based on light emitting diodes and/or basedon laser diode devices.

In certain embodiments provided by the present disclosure, light sourcescomprise at least one first LED emission source characterized by a firstemission; and at least one second LED emission source characterized by asecond emission; wherein the first emission and the second emission areconfigured to provide a first combined emission and a second combinedemission; the first combined emission is characterized by a first SPDand fractions Fv1 and Fc1; the second combined emission is characterizedby a second SPD and fractions Fv2 and Fc2; Fv1 represents the fractionof power of the first SPD in the wavelength range from 400 nm to 440 nm;Fc1 represents the fraction of power of the first SPD in the wavelengthrange from 440 nm to 500 nm; Fv2 represents the fraction of power of thesecond SPD in the wavelength range from 400 nm to 440 nm; Fc2 representsthe fraction of power of the second SPD in the wavelength range from 440nm to 500 nm; the first SPD and the second SPD have a color renderingindex above 80; Fv1 is at least 0.05; Fc2 is at least 0.1; and Fc1 isless than Fc2 by at least 0.02. Other values are possible for Fc1, Fc2,Fv1, and Fv2, such as 0.001, 0.005, 0.01, 0.05, 0.1, 0.2, or greater andany value inbetween.

In certain embodiments of a light source, the first combined emission ischaracterized by a first circadian stimulation; the second combinedemission is characterized by a second circadian stimulation; and thesecond circadian stimulation is at least twice the first circadianstimulation.

In certain embodiments of a light source, the first LED emission sourcecomprises at least one LED characterized by a peak emission in the range405 nm to 430 nm.

In certain embodiments of a light source, the first emission and thesecond emission are configured to provide a third combined emission; thethird combined emission is characterized by a third SPD, a fraction Fv3,a fraction Fc3, and a third circadian stimulation; Fv3 represents thefraction of power of the third SPD in the wavelength range from 400 nmto 440 nm; Fc3 represents the fraction of power of the third SPD in thewavelength range from 440 nm to 500 nm; the third SPD has a coloringrendering index above 80; and the first circadian stimulation and thethird circadian stimulation are different.

In certain embodiments of a light source, the second emission comprisesblue emission from a wavelength down-conversion material.

In certain embodiments of a light source, the second emission comprisesdirect blue emission from an LED.

In certain embodiments of a light source, one of the combined emissionsinduces a circadian stimulation similar to a circadian stimulation of aD65 reference illuminant.

In certain embodiments of a light source, one of the combined emissionsinduces a circadian stimulation that is less than a circadianstimulation of a CIE A reference illuminant.

In certain embodiments of a light source, the at least one first LEDemission source and the at least one second LED emission source areconfigured in an intermixed physical arrangement.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity within the white lightbounding region 514 of FIG. 5B.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity bounded by ±0.005 of aPlanckian loci and by ±0.005 of a minimum-hue-shift curve in a CIEchromaticity diagram.

In certain embodiments of a light source, each of the first SPD and thesecond SPD is characterized by a chromaticity within +/−five Du′v′points of a Planckian loci.

In certain embodiments of a light source, exposure of a subject to thesecond SPD with an illuminance of 100 lx for ninety minutes results in asuppression of blood melatonin concentration in the subject of at least20%.

In certain embodiments of a light source, exposure of a subject to thefirst SPD with an illuminance of 100 lx for ninety minutes results in asuppression blood melatonin concentration in the subject of at most 20%.

In certain embodiments of a light source, Fc1 is at most 0.06

In certain embodiments, a display system comprises a first LED emissionsource characterized by a first emission; and a display configured toemit a first SPD characterized by a first fraction Fv1 of power in therange 400 nm to 435 nm; wherein, the display system is characterized bya color gamut of at least 70% of NTSC; the first SPD is substantiallywhite with a CCT in a range from 3000K to 9000K; and Fv1 is at least0.05.

In certain embodiments of a display system, the display comprises anemission spectrum characterized by a circadian stimulation that is lessthan a circadian stimulation of a reference illuminant having the sameCCT.

In certain embodiments of a display system, the display system furthercomprises a color filter set and a liquid crystal display.

In certain embodiments of a display system, the first SPD ischaracterized by a peak in the wavelength range from 400 nm to 435 nm ata wavelength w; the color filter set comprises a blue filtercharacterized by a maximum transmission Tm, and by a transmission Tw atwavelength w; and Tw/Tm>0.8.

In certain embodiments, a display system further comprises a second LEDemission source characterized by a second emission, wherein a ratio ofthe first emission and the second emission are configured to be adjustedto change a circadian stimulation.

In certain embodiments of a display system, the display system isconfigured for use with a TV, desktop PC, notebook PC, laptop PC,tablet, smartphone, MP3 player.

In certain embodiments of a display system, less than 5% of the power ofthe first SPD is in a wavelength range from 440 nm to 500 nm.

In certain embodiments, a light source comprises an LED deviceconfigured to emit a primary emission; one or more wavelength conversionmaterials optically coupled to the primary emission; wherein a portionof the primary emission is absorbed by the wavelength conversionmaterials to produce a secondary emission; wherein a combination of theprimary emission and the secondary emission produces white lightcharacterized by an SPD having a CCT and a color rendering index;wherein at least 5% of the SPD is in a wavelength range from 400 nm to435 nm; wherein a circadian stimulation of the SPD is less than 80% of acircadian stimulation of a reference illuminant having the same colortemperature; and wherein the white light is characterized by a colorrendering index above 80.

In certain embodiments, of a light source, the primary emission ischaracterized by a peak wavelength between 405 nm and 425 nm.

In certain embodiments, a lighting system comprises an LED deviceconfigured to emit a primary emission characterized by a primary SPD; atleast one phosphor optically coupled to the primary emission, whereinthe at least one phosphor is characterized by saturable absorptionwithin a blue-cyan wavelength region; wherein the LED device isconfigured to be controlled by a power signal configured to dim theprimary emission; wherein at a first power level the system emits afirst SPD characterized by a first fraction fc1 of spectral power in awavelength range from 440 nm to 500 nm and a first CCT; wherein at asecond power level the system emits a second SPD characterized by asecond fraction fc2 of spectral power in a wavelength range from 440 nmto 500 nm and a second CCT; and wherein the second power level is lessthan the first power level and the second fraction fc2 is less than 80%of the first fraction fc1.

In certain embodiments of a lighting system, the second CCT is at least500K less than the first CCT.

In certain embodiments of a lighting system, at least 5% of the primarySPD is in a wavelength range from 400 nm to 435 nm.

Some embodiments make use of filters. For instance, one or more filterscan be employed in order to remove radiation that would cause circadianstimulation. Considerations with respect to such filters are discussedherein-below. In these discussions, the acronym CS is used to refer tocircadian stimulation and the acronym CSR is used to refer to thecircadian spectral range of maximal stimulation.

The disclosure herein shows how the combination of violet LEDs andproperly-chosen phosphors enabled a reduction of CS by an order ofmagnitude or more as compared to conventional light sources. Such adramatic reduction can be achieved by removing radiation in the CSR. Insome cases it is desirable to further reduce the CS, for instance by twoorders of magnitude or more. For instance, this is the case in anenvironment where there is a large illuminance (such as several hundredsor thousands of lux). Indeed, in this case the circadian response is“saturated”. As one example, melatonin suppression can be measured anddeemed complete after 90 minutes. Reducing the CS by only one order ofmagnitude still yields significant suppression. In some cases, it isdifficult to attain such low levels of CS by combining a violet LED andconventional phosphors because the violet LED and the yellow/greenphosphor have residual emission tails in the CSR.

Further reduction of CS can be obtained by the use of filters thatremove radiation in the CSR. However, the filters should be designedsuch that the resulting quality of light is still acceptable. It ispossible to substantially filter out any light below say 500 nm, thusachieving low CS, however that spectrum would be observed as a veryundesirable quality of light (e.g., in terms of chromaticity andCRI)—for instance, it would likely have a pronounced yellow tint. Forquality or light reasons, it is desirable to maintain a chromaticityon-Planckian or near-Planckian, and a CRI of 80 or above. The followingdiscussions provide further details of practical implementation ofreduced CS embodiments.

The following discussions use a simplified figure of merit for circadianstimulation. In particular, the fraction of the SPD in the CSR isconsidered. For the sake of teaching how to make and use theseembodiments, consider the range 430-490 nm as the CSR in the followingillustrations. The discussion can easily be adapted to other ranges (orto more complex responses, such as an action spectrum with a given shapein a given spectral range). For illustration, a conventional blue-pumpedLED with a CCT of 3000K and a CRI of 80 has about 12% of its power inthe CSR.

FIGS. 16A through FIG. 21B present techniques for making and usingcircadian filters, according to certain specifications. Using varioustechniques, notch filters can be designed to block light in a selectedwavelength range, while providing high transmission in other ranges. Forinstance, it is common to stack multilayers of materials with varyingoptical indices to obtain notch filters. A common choice is a SiOx/NbOxstack (of course other materials can be considered, such as TiOx, TaOx,etc.). These stacks can be designed by optical software, using arelevant figure of merit such as low transmission in the CSR.

The depictions of FIG. 16A through FIG. 16D show such an example. FIG.16A describes a dielectric stack deposited on a glass substrate(materials and thicknesses in nm). FIG. 16B shows the correspondingtransmission curve. FIG. 16C shows how the initial SPD of a light sourceis modified into a filtered SPD when the filter is placed in front ofit. FIG. 16D indicates corresponding colorimetric properties of theinitial spectrum and of the filtered spectrum.

In this example, the initial spectrum is targeted to be on-Planckian at3000K. The filter induces a slight chromatic shift (approximately 7Du′v′ points). The CRI is maintained at 80. The effect on chromaticshift and CRI is moderate because the initial spectrum already hadrelatively little radiation in the CSR. Despite this modest effect onchromaticity, the reduction of power portion (e.g., percentage) in theCSR is substantial (more than tenfold). In comparison to a standardblue-pumped LED with the same CCT and CRI, the reduction in power in theCSR is sixty times. Other filter designs can achieve further reduction,or provide reduction in a different wavelength range as desired.

In various cases, one may want to design a filter such that the filteredSPD is on-Planckian. This can be achieved by starting from anoff-Planckian initial SPD so that the chromatic shift of the filterbrings the SPD on-Planckian. This is achievable by selecting the rightchoice and amount of phosphors to achieve a given chromaticity afterfiltering. FIG. 17A and FIG. 17B illustrates this. Here the dielectricfilter is the same as in the FIG. 16 series, but the initial SPD hasbeen tuned so that the filtered SPD would be on-Planckian. FIG. 17Ashows the initial SPD and the filtered SPD. FIG. 17B shows thecorresponding colorimetric properties. Here again, the filtered SPD hasan order of magnitude less power in the CSR than the initial SPD.

One design technique starts with an on-Planckian light source andconstructs a filter which has the proper transmission at all wavelengthsto maintain the initial SPD's chromaticity. Also note that in theforegoing, the initial SPDs have little radiation in the CSR, thereforethe filtering has a very small impact on the system's efficiency, whichis desirable. Further, one may take into account the transmission andabsorption of various other elements in the optical system (lenses,reflectors, etc) such that the final spectrum emitted by the system,taking into account the transmission of the whole system (including thefilter), is on-Planckian or at a selected chromaticity. Taking suchtransmissions into account is well-known in the art.

Dichroic filters are especially suited when the light source is fairlydirectional, because transmission usually varies with angle. Thereforedichroic filters can be easily adapted to narrow-beam light sources. Forinstance dichroic filters can be used in conjunction with a spot lamp(such as a 4°, a 10° or a 20° spot). Such dichroic filters may be addedto any existing light source. As discussed above, the filter can bedesigned to maintain the chromaticity of the light source (and otherproperties such as CRI, etc.). In some embodiments, the spot lamp can beconverted between a circadian-stimulating source and acircadian-friendly source by addition of the filter. This filter can becombined with a diffuser to obtain a wider beam angle.

In other cases one may want to use a non-directional light source. FIGS.18A and 18B show the effect of incidence angle for the filter of FIG.16B coupled to the initial spectrum of FIG. 16C. FIG. 18A shows thetransmission versus angle for the filter of the FIG. 16 series. The stopband shifts with incidence angle, as is typical in dichroic stacks.Table 18B shows how resulting colorimetric quantities can vary withangle. The CRI and Du′v′ vary rather strongly between 0° and 40°. Thusthis filter would be suitable for a 10° beam angle, but less so for a40° beam angle.

By applying design techniques to the foregoing observations, thefiltering may be adapted to lessen this angular variation. This can beachieved by designing a dichroic stack where the figure of merit has lowangular variation. FIGS. 18C-18D show such an embodiment.

In particular, FIG. 18C shows the transmission versus angle for adichroic filter that has been designed for low transmission in the CSRfor angles between 0° and 40°. The corresponding table (FIG. 18D) showsthat the colorimetric quantities (Ra, cct, Du′v′) show less variationwith angle than previous embodiments (using the same initial spectrum ofFIG. 16C).

FIG. 18E shows the corresponding stack's details (materials andthicknesses in nm). The total thickness of the filter depicted inembodiment 18E00 is less than 4 um. Further improvements could beachieved by allowing a thicker filter.

For non-directional light sources, another approach is to use a filterwhich is inherently non-directional, for instance an absorbing filter.Many exiting color filters (such as commercial polyester filters)incorporate dyes with absorption in the CSR. Use of such a filter yieldsangle-independent absorption. In some embodiments, the filter and theSPD are designed in conjunction, in order to obtain a desiredchromaticity for the filtered spectrum (with the same procedure used inFIG. 2).

In some cases the system has a mechanical component such that the filtercan be moved in various directions relative to the light source, andsuch movement can be performed manually or automatically (or both). Forinstance, the filter may be moved in and out of the beam of the lightsource to control filtering of the spectrum.

In the case of a lighting application, the filter can be placed atvarious positions in the system. FIG. 19A through 19C showscross-sections of spot lamps with a lens 1902, an LED 1908, a heatsink1096, and a filter 1904 placed at various positions in the system. Forinstance, the filter may be placed on top of the LED module (see FIG.19A), at the exit port of the lens (see FIG. 19B) or at the entranceport of the lens (see FIG. 19C).

In a linear troffer 20A00, the filter may be placed in front of the LEDsor at the exit port of the luminaire. FIG. 20A shows the cross-sectionof a troffer with linear LED strips 2002 and a filter 2004 around theLED strips. FIG. 20B shows a linear strip troffer 20B00 with the filter2005 at the luminaire's exit port.

FIG. 20C depicts an A-lamp bulb with a filter 2002. The embodiment isuseful for general illumination purposes. In the case of an A-lamp (orother consumer lamps such as BR lamps, for instance) the filter may beplaced at various positions in the system. It may be placed in a remoteconfiguration (in-between the LED emitter and a protective envelope) asshown in FIG. 20C. It may also be placed in the vicinity of the LEDemitter, or integrated with the protective envelope.

In various embodiments, the system may mix standard sources with highcircadian stimulation and circadian-friendly sources with a filterachieving very low circadian stimulation.

As already mentioned, the discussion above uses a simplistic metric(fraction of SPD in the CSR). Other metrics can be used to design thefilter, such as the fraction of power Fv in the violet range (forinstance 400-440 nm), the fraction of power Fc in the cyan range (forinstance, 440-500 nm) and their ratio. For instance, for the filteredspectrum of FIG. 2a , Fv=0.256, Fc=8E-4 and Fc/Fv=0.003. Other cyanranges (such as 430 nm-500 nm) could also be used. Based on theteachings of this invention, one skilled in the art will know how toselect light sources and wavelength converters to obtain spectra with agiven SPD fraction in a given range (for instance, a low or highfraction of total SPD power in a given range) and given quality-of-lightmetrics.

FIG. 21A and FIG. 21B depict two displays architectures using LEDscoupled to waveguides. In each case, a filter is present to removeradiation in the CSR. In the case of FIG. 21A, the filter is placed atthe coupling facet. In the case of FIG. 21B, the filter is placed in alayer parallel to the waveguide (for instance, it may be coated on theoutput facet of the waveguide, or it may be combined with anotherelement of the display such as the RGB filters).

Embodiments using waveguide coupling may be useful for displayapplications (such as screens, phones, tablets, and other lighteddevices), but also for general lighting applications in waveguide-basedluminaires.

FIGS. 22 through FIG. 24 present variations using accessories (e.g.,filters) in combination and/or in combination with LED lamps. Filterscan be implemented with magnetic or other mating devices, and filterscan be designed or combined to project emanated light in selectedpatterns of intensity. Strictly as an example, exploded perspective view2200 depicts an MR-16 LED lamp 2202 comprising a heatsink 2220, a lens2206, and first and second instances of magnets 2202 where the firstmagnet 2202 ₃ is affixed to the lens, and the second magnet 2202 ₄ isaffixed to an accessory 2204. The accessory can implement filtersdesigned to project emanated light in selected patterns of intensity.For example, FIG. 23 depicts a side view 2302 of a focus spot, and FIG.24A depicts a side view 2402 of a diffused flood lamp pattern. FIG. 24Bdepicts a side view 2404 of a medium spot pattern.

FIG. 25A to FIG. 25E illustrate additional advantages of combining afilter with a spectrum which already has only a small portion ofradiation in the CSR. FIG. 25A and B compare two filtered spectra. Inthese figures a CSR of 430-490 nm is assumed and the filter cuts off allradiation in this CSR. FIG. 25A is a standard source (specifically, astandard blue-pumped LED source) with a filter; although the presence ofthe filter ensures little radiation in the CSR, it also induces asignificant loss of optical power (black region of FIG. 25A): 11% of theoptical power is lost due to filtering. Other standard light sources,such as filament lamps, would incur similar losses with the same filter.In contrast, FIG. 25B shows an embodiment of the invention, combining aspectrum with little radiation in the CSR and a filter cutting off allresidual radiation in the CSR. In this case, only 3% of the opticalpower in the spectrum is lost due to filtering. Therefore, embodimentsof the invention may be more radiation-efficient than standard lightsources using a filter to reduce circadian stimulation. For example, forthe same starting radiated power levels for each of the light sourcescorresponding to FIGS. 25A and 25B, after filtering, more of theoriginal radiation is retained for FIG. 25B as compared to FIG. 25A. Inaddition, since so much radiation is removed for the case of FIG. 25A, alarge color shift is incurred (e.g., the light source is no longerwhite), which color shift is not easily corrected. In contrast, for thecase of FIG. 25B, only a small chromaticity shift is caused byfiltering, which can be easily corrected by slight compensatingmodifications to the primary violet light emission and/or the phosphoremission.

FIG. 25C and FIG. 25D are similar to the previous figures, but considera slightly narrower CSR of 440-480 nm. Here again the filter cuts offall radiation in the CSR. When applied to a conventional source, thefilter cuts off 8% of the total spectral power whereas when applied to aspectrum with little radiation in the CSR, only 1% of the total spectralpower is lost. Therefore, energy savings can be achieved by embodimentscombining a spectrum with little radiation in the CSR and a filterblocking light in the CSR, regardless of the specific value of assumedfor the CSR.

In addition, the spectra of FIGS. 25A to 25E differ in theirchromaticity. This is summarized in the table of FIG. 25E which showsthe color coordinates (u′v′) and the distance to the Planckian locus(Duv), for unfiltered spectra and for spectra filtered by the twofilters considered above. Before filtering, both the conventionalspectrum and the embodiment of the invention (with little radiation inthe CSR) have a chromaticity which is close to the Planckian locus (thevalue of Duv is small). Application of the filter induces a chromaticshift, but this shift is more moderate for embodiments of the inventionthan for standard sources, which may be desirable. The chromatic shiftsdisplayed by filtered standard sources correspond to a pronouncedyellowish tint which may be undesirable.

As already mentioned, specific embodiments of the invention furtherreduce the value of Duv by combining a spectrum which is initiallyoff-Planckian with a filter so that the resulting embodiment is nearlyon-Planckian. By the same approach, other embodiments may also aim for afinal chromaticity which is not on the Planckian locus, but is forinstance below the Planckian locus instead.

In some embodiments of the invention, the optical power lost due to theaddition of a filter is less than 8%, less than 5%, less than 3% or lessthan 1%. In some embodiments of the invention, the chromatic shift (inunits of (u′v′)) between the unfiltered and the filtered spectra is lessthan 10E-3, less than 2E-3, less than 1E-3. In some embodiments of theinvention, the distance Duv to the Planckian locus of the filteredspectrum is less than 10E-3, less than 2E-3, less than 1E-3.

FIG. 26A presents an exploded view 26A00 of an LED lamp used with aninterchangeable retaining ring kit for mating to an LED lamp heatsink.As an option, the present exploded view 26A00 may be implemented in thecontext of the architecture and functionality of the embodimentsdescribed herein. The depicted exploded view 26A00 or any aspect thereofmay be implemented in any desired environment.

In some embodiments, aspects of the present disclosure can be used in anassembly. As shown in FIG. 26A, the assembly comprises:

-   -   a screw cap 2628    -   a driver housing 2626    -   a driver board 2624    -   a heatsink 2622    -   a metal-core printed circuit board 2620    -   an LED lightsource 2618    -   a dust shield 2616    -   a lens 2614    -   a reflector disc 2612    -   a magnet 2610    -   a magnet cap 2608    -   a trim ring 2606    -   a first accessory 2604    -   a second accessory 2602

As shown, the heatsink 2622 and trim ring 2606 can be mated together. Insome cases, the trim ring is mated to the heatsink using threads thatare present on the trim ring, or using threads present in screwfasteners. Any fastener can be used to affix the trim ring to theheatsink, and different fastening techniques may offer varying degreesof thermal conductivity with the heat sink. A gasket may be used to forma seal between the heat sink and a trim ring.

The components of assembly 26A00 may be described in substantial detail.Some components are ‘active components’ and some are ‘passive’components, and can be variously-described based on the particularcomponent's impact to the overall design, and/or impact(s) to theobjective optimization function. A component can be described using aCAD/CAM drawing or model, and the CAD/CAM model can be analyzed so as toextract figures of merit as may pertain to e particular component'simpact to the overall design, and/or impact(s) to the objectiveoptimization function. Strictly as one example, a CAD/CAM model of atrim ring is provided in a model corresponding to the drawing of FIG.26C.

FIG. 26B shows a selection of rings of a kit 26B00 showing an example ofinterchangeable retaining ring kit for mating to an LED lamp heatsink.As an option, the present selection of rings of a kit 26B00 may beimplemented in the context of the architecture and functionality of theembodiments described herein. The depicted selection of rings of a kit26B00 or any aspect thereof may be implemented in any desiredenvironment.

As shown, a set of trim rings may be combined into a kit such that oneor another trim ring can be selected for use with a particular lamp anda particular luminaire. For example the kit of FIG. 26B (top), containsthree trim rings as follows:

-   -   A thin trim ring (top left) for use with a PAR30L form factor        LED lamp and a luminaire of type PAR30L.    -   A thin trim ring (top center) for use with a PAR30L form factor        LED lamp and a luminaire of type AR111.    -   A thin trim ring (top right) for use with a PAR38 form factor        LED lamp and a luminaire of type PAR38.

FIG. 26C includes a mechanical drawing inset showing detail of anexample component within an interchangeable retaining ring kit formating to an LED lamp heatsink, according to some embodiments.

A particular trim ring may have a mechanical design so as to provide apositive contact with adjacent components. In particular, a trim ringmay contain undulations or detents to facilitate thermal conductivitybetween the heatsink and any surrounding structures, possibly includingthe housing of the luminaire.

The particular size and shape of the trim ring may vary to facilitateany particular function, and/or the particular size and shape of thetrim ring may vary to accommodate snap-on or other field-replaceableaccessories. Examples of the foregoing functions include:

-   -   Holding the lens in place within the assembly.    -   Supporting a snap-on or other field-replaceable diffuser.    -   Enhance the function of the heatsink (e.g., conduct heat from        the heatsink to other structural members and to the air        interface).    -   Provide a mechanical mating between an American National        Standards Institute (ANSI) ANSI-standard lamp and a compliant        luminaire.    -   Provide a mechanical mating between an ANSI-standard compliant        luminaire and a lamp.    -   Provide a mechanical mating between an International        Electrotechnical Commission (IEC) IEC-standard lamp and a        compliant luminaire.    -   Provide a mechanical mating between an IEC-standard luminaire        and a compliant lamp.    -   Provide a mechanical mating between a National Electrical        Manufacturers Association (NEMA) NEMA-standard luminaire and a        compliant lamp.    -   Provide a mechanical mating between a NEMA-standard compliant        luminaire and a NEMA-standard lamp.

FIG. 26C includes a mechanical drawing inset 26C00 showing detail of anexample component within a interchangeable retaining ring kit for matingto an LED lamp heatsink. As an option, the present mechanical drawinginset 26C00 may be implemented in the context of the architecture andfunctionality of the embodiments described herein. The depictedmechanical drawing inset 26C00 or any aspect thereof may be implementedin any desired environment.

Following the foregoing, a trim ring may have certain specifications formating, and such specifications may be defined in conjunction with themechanical specifications of a heatsink. For example, protrusions and/ordepressions, or flanges and/or openings, or zig-zag undulations and/orzag-zig undulations can be specific to a trim ring, and/or a heatsink.Several embodiments can be described as follows:

-   -   Embodiment 1. An interchangeable retaining ring kit for mating        to an LED lamp heatsink, comprising:        -   a first trim ring having a first form factor; and        -   a second trim ring having a second form factor.    -   Embodiment 2. The interchangeable retaining ring kit of        embodiment 1, wherein the first trim ring has protrusions        configured to mate mechanically to depressions in the LED lamp        heatsink.    -   Embodiment 3. The interchangeable retaining ring kit of        embodiment 1, wherein the first trim ring has depressions        configured to mate mechanically to protrusions in the LED lamp        heatsink.    -   Embodiment 4. The interchangeable retaining ring kit of        embodiment 1, wherein the first form factor has a first diameter        and the second form factor has a second diameter, wherein the        first diameter and the second diameter are different.    -   Embodiment 5. The interchangeable retaining ring kit of        embodiment 1 wherein the first form factor has a first thickness        and the second form factor has a second thickness, wherein the        first thickness and the second thickness are different.    -   Embodiment 6. The interchangeable retaining ring kit of        embodiment 1, further comprising at least one fastener to affix        the first trim ring to the LED lamp heatsink.

Circadian filters can be used in combination with any lamp types, and/orwith any mating or retaining structures.

FIGS. 27A and 27B provide images of a lamp system having a trim ringinstalled. As shown in FIG. 27A, a PAR30 lamp is fitted with a firsttrim ring 2702 from a kit 11800. The assembly 27A00 can be installedinto a luminaire. As shown in FIG. 27B, a PAR38 lamp is fitted with asecond trim ring 2704. The assembly 27B00 can be installed into aluminaire. Both the first trim ring 2702 and the second trim ring 2704are delivered in a kit.

The foregoing embodiments describe a lamp system and techniques formaking and using an interchangeable retaining ring kit. At least some ofthe components of the kit serve to mate to an LED lamp heatsink. In someassemblies, the lamp system comprises an LED lightsource configured tobe disposed at least partially within the LED lamp heatsink, which isthen fitted with a first trim ring having a first form factor (e.g., toconform to a first ANSI form factor). The interchangeable retaining ringkit comprises a second trim ring having a second form factor (e.g., toconform to a second ANSI form factor).

To implement some embodiments of the invention, care is taken such thatno element in the system provides unwanted emission in the CSstimulation range. In particular, the absence of fluorescent whiteningagents (FWAs) may be important. FWAs are particles that can absorbshort-wavelength radiation (such as ultraviolet radiation and violetlight) and emit fluorescence in the range 440-480 nms; they typicallyabsorb light at wavelengths shorter than 430 nm. They are commonly usedin a variety of white materials to enhance the perception of whiteness.Embodiments of the invention comprise an LED emitter which emits violetlight. It may be unwanted that such light substantially interact withFWAs as this may result in substantial emission in the CS range.Therefore, it may be desirable to design a system that does not containa significant presence of FWAs which can interact with light and createfluorescence in the CS spectral range. Similar considerations apply toother fluorescent materials similar to FWAs.

A possible way to test for the effect of FWAs is as follows. One maymeasure the direct emission of the LED module outside the system,characterized by a normalized spectral power distribution SPD_1. One maythen measure the emission of the full system, characterized by anormalized spectral power distribution SPD_2. The ratio R=SPD_2/SPD_1can then be computed to check for the presence of fluorescence. In theabsence of any fluorescence and if the system's optical response isspectrally flat, R should be equal to one. In a more realistic case, thesystem shows absorption with slight wavelength dependence, and R is asmoothly varying function of wavelength. However, in the presence offluorescence from FWAs, R shows a pronounced peak with a value aboveunity in the blue range—this is due to the lack of blue light in SPD_1and the higher presence of fluorescent blue light in SPD_2.

FIG. 28A and FIG. 28B present experimental results which illustrate thiseffect. FIG. 28A shows a superposition chart 28A00 that plots a finalSPD 1604 over an initial SPD 1602. SPD_1 (see initial SPD 1602) is basedon an LED emitter. As shown, SPD_1 has relatively little light in therange 430 nm-480 nm. FIG. 28A also shows SPD_2 (see final SPD 1604) thatis measured when the LED emitter is placed in a lighting fixture thatcontains FWAs. SPD_2 has more light in the same range due tofluorescence. SPD_1 and SPD_2 have been normalized to their peak valuein the green-red range for easier comparison. FIG. 28B shows thecorresponding ratio R. R shows a pronounced peak centered near 460 nm,which evidences the presence and effect of FWAs on the system.

Another way to ascertain the absence of a significant effect from FWAsis simply to measure the net spectrum emitted by the complete lightingsystem and to ascertain that it does not contain unwanted radiation inthe CS spectral range.

Some embodiments are related to lighting products such as A lamps or BRlamps. Such lamps are common in consumer homes. Their typical CCT is2700K (for instance standard incandescent), with other common valuesranging from 3000K (for instance halogen lamps) to 2500K (for lampsincandescent dimmed to 10-20% of its full optical power).

FIGS. 29-45 compare properties of various spectra, including blackbodyradiators and embodiments. The shown SPDs have been normalized to aluminous flux of 100 lm. Tables indicate corresponding radiometric andcolorimetric properties. It has already been demonstrated above thatlight sources such as filament lamps and conventional LED lamps cancause unwanted circadian stimulation. The discussion below providesadditional quantitative examples, and contrasts these with embodiments.

FIGS. 29, 32, 35 and 39 are for blackbody radiators and arerepresentative of conventional filament lamps. The corresponding tablesshow that, when going from 2700K to 2200K, the total power in the range450-490 nm is roughly halved. In a scenario where a user dims a light to20% of its full optical power, which shifts the CCT from 2700K to 2200K,the circadian stimulation in the range 450-490 nm is therefore dividedby 10 (a factor of 5 for total flux, and a factor of 2 for relativefraction of power in the relevant spectral range).

FIGS. 36 and 40 show conventional LED spectra. The total power in therange 450-490 nm is roughly similar to that of filament lamps,indicating a similar CS—which can be called a “regular CS”. Similarconclusions are reached when assuming other CS ranges of action, such as440-500 nm.

Embodiments of the invention shown on FIGS. 30, 31, 33, 34, 37, 38, and41 have a power in the range 450-490 nm which is about 10% of the powerof a blackbody radiator of the same CCT and same luminous flux.Therefore, for a given CCT, circadian stimulation is reduced by a factorof 10. Other CS ranges of action give slightly different results—forinstance the range 440-500 nm leads to a reduction by a factor of five.In general, such reductions in CS are termed as sources with “low CS”.In addition, as mentioned elsewhere herein, a more complex metric may beused than the fraction of the SPD in a given range. Rather, a circadianaction spectrum may be chosen and integrate the SPD using this actionspectrum as a weighing function, thus obtaining the “circadianstimulation” described elsewhere. This more sophisticated figure ofmerit leads to the same quantitative conclusions as that describedherein: it is possible to design a light source which reduces the“circadian stimulation” by one order of magnitude, two orders ofmagnitude or more versus a conventional light source, and maintainsaspect of quality-of-light (CCT, chromaticity, Ra, R9 . . . )

A low CS can also be quantified by the amount of optical power (for aSPD normalized to an illuminance of 1001m) in a CS wavelength range ofinterest, such as 430-510 nm, 440-500 nm or 450-490 nm. A low spectralcontent in a given CS range may correspond for instance to less than 10mW, less than 5 mW, less than 2 mW. This can be compared to values ofabout 20-40 mW for blackbody radiator at 2700K.

FIG. 46 shows how a 3000K halogen undergoes a CCT shift as it is dimmed.The CCT is indicated as a function of the input electrical power. Otherfilament lamps, such as incandescent lamps, also undergo a similarshift.

FIG. 47 shows how a 3000K halogen undergoes a CCT shift as it is dimmed.The CCT is indicated as a function of the emitted optical power. Otherfilament lamps, such as incandescent lamps, also undergo a similarshift.

Some embodiments of the invention approximate the CCT shift as thelighting level is dimmed. This can follow various curves such as arepresented below in FIG. 46 and FIG. 47. In this case, for any dimminglevel, the embodiments have a CS which is about ten times lower thanconventional lamps.

Some spectra shown on FIGS. 29-45 demonstrate that embodiments canachieve a CRI Ra above 80, for CCTs in the range 2200-3000K. Otherspectra shown on FIGS. 29-45 demonstrate that embodiments can achieve ahigh deep-red rendering index R9 in the range 96-97, for CCTs in therange 2200-3000K. These embodiments were obtained by tuning the centerwavelength of the red phosphor. Further tuning can be achieved byselecting the shape and center wavelength of various phosphors.Therefore, embodiments of the invention can achieve good or excellentcolor rendering while maintaining a low CS.

When comparing embodiments to standard LED sources radiators with thesame luminous flux, it is possible to consider the power in a givenspectral range or the percentage of the SPD in a given spectral range.When comparing embodiments to blackbody radiators with the same luminousflux, it is most appropriate to consider the power in a given spectralrange (percentage of the SPD is less practical due to the large infraredtail of blackbody radiators).

In some embodiments, the invention is a lamp with two independentstrings of LEDs. One string has a CCT of 2700K and a low CS, similar tothe spectrum of FIG. 37. The other has a CCT of 2200K and a low CS,similar to the spectrum of FIG. 30. Upon dimming the lamp, the CCTshifts according to curves similar to those of FIG. 46 and FIG. 47; thisis achieved by driving the power in each string accordingly. At alldimming powers, CS is low.

In other embodiments, the invention is a lamp with two independentstrings of LEDs. One string has a CCT of 2700K and a regular CS—this canbe achieved by using any standard white LED with a usual amount ofblue-cyan radiation. The other string has a CCT of 2200K and a low CS,similar to the spectrum of FIG. 30. Upon dimming the lamp, the CCTshifts according to curves similar to those of FIG. 46 and FIG. 47; thisis achieved by driving the power in each string accordingly. At fullpower, light is emitted from the first string and CS is high; at lowpower (for instance, 10% or 20% optical power), light is emitted fromthe second string and CS is low.

In other embodiments, different combinations of CCTs and CS can be used.

In other embodiments, only one string is present. It has a CCT of 2700Kand a low CS, similar to the spectra of FIG. 37-38. The lamp alwaysprovides a low CS.

In some applications, lamps with a varying spectrum are desirable. Thisincludes variations in CCT, intensity, etc. This can be done, forinstance, with a three-color RGB LED lamp where the three channels aredriven separately and mixed to generate a desired spectrum. However,although they are able to produce many different spectra, suchhighly-configurable tunable spectrum sources are expensive and sometimescomplex to control. In some cases, only a few specific spectra aredesirable—for instance white spectra at a few or several CCTs. Oneexample is the 3-way incandescent bulb. Control of a 3-way bulb issimple and inexpensive, and often is based on an inexpensive mechanicalselector. 3-way LED lamps can be useful in various situations where asimple way to switch between emitted spectra is desired. In the contextof the invention, 3-way lamps can be used to switch betweencircadian-friendly spectra and other spectra.

In some embodiments, the lamp is a 3-way lamp. It includes two strings.One has a regular CS, and the other has a low CS. As the 3-way switch iscycled, one or the other filament is turned on. In some embodiments thetwo strings have the same CCT. In some embodiments the two strings havea different CCT—for instance, the first string has a CCT of 3000K and aregular CS; the other has a CCT of 2500K and a low CS. In someembodiments there is an indicator on the bulb which indicates whichstring is active. In some embodiments, more than two strings arepresent. In some embodiments the power emitted by the two strings isdifferent—for instance the first string has a regular CS and a firstlight output, the second string has a low CS and a second output whichis half the first output.

In further embodiments, control is provided through a computer interfacerather than by a manual control (such as a dimmer or switch). Saidcontrol may correspond to switching between two strings of LEDs, such asstrings of different CCTs or strings of different CS. For instance,control can be provided through a smartphone or another smart device(watch, tablet . . . etc.). Several embodiments of 3-way lamps are shownand discussed as pertaining to FIG. 48A through 48E.

In some cases the control is automated. For instance, transition from astring of high CS to a string of low CS happens at a given time of theday.

In some embodiments of the invention, some of all of the light isprovided by a narrow emitter such as a laser, a laser diode (LD), or asuperluminescent LED.

In an embodiment, violet light is provided by a laser diode; the laserfurther pumps a green and a red phosphor. This results in a spectrumwith no blue light and a sharp cutoff of violet light, thanks to thenarrow emission spectrum of the LD. FIG. 45A shows such an embodiment,on-Planckian with a CCT of 2700K, where the laser wavelength is 420 nmand the laser line's width is 3 nm. Other wavelengths can be used; otherwidths (such as 1 nm or less) can be used with very similar results.Likewise, slightly broader widths (as might be obtained by asuperluminescent LED) can also be used with very similar results. FIG.42A also shows that such laser-based embodiments can reach CRI Ra valuesabove 80. FIG. 43A shows a similar embodiment with a shifted redphosphor, having a high R9 value of 97.

In the hypothesis that the CS action spectrum is still significant inthe violet range (for instance down to 430 nm or 425nm), suchembodiments are desirable: they enable on-Planckian white light withgood color rendering and with very little CS.

Further, embodiments may utilize a violet laser and a green/yellowlaser. FIG. 44 shows such an embodiment, on-Planckian with a CCT of2700K, where one laser has a wavelength of 420 nm and the other awavelength of 518 nm. In this case, for a 100 lm spectrum, the totalpower in the range 422-516nm is less than 2 mW, as compared to 51 mW fora 2700K Blackbody radiator. Therefore, even in the hypothesis of a verybroad CS action spectrum, this SPD would cause minimal CS.

Yet other embodiments use three laser lines (violet, green/yellow andred) or more. FIG. 45 shows such an embodiment.

Some embodiments employ both a violet LD and a blue LD, or a violet LDand a blue LED. In such embodiments, the ratio of power driving theviolet and the blue emitter may be modulated in order to tune the CS ofthe emitted SPD.

In embodiments combining lasers and phosphors, the phosphor may beconfigured in a remote configuration; or it may be configured inproximity to the LD that pumps it. For instance, in a given embodiment,a violet LD pumps a red phosphor and a green phosphor; the mixture ofthe violet, green and red light emits the embodiment's SPD. In anotherembodiment, a violet LD pumps a red phosphor and a green LD doesn'tsignificantly pump the red phosphor. In yet another embodiment, a greenLD pumps a red phosphor and a violet LD doesn't significantly pump thered phosphor.

Although light sources using one or more laser lines are known in theart, embodiments are distinguished by their low CS. Indeed, if CS werenot considered, the natural choice for one skilled in the art would beto employ a LD with a wavelength of about 440-470 nm to optimize theluminous efficacy (LE). This is demonstrated in Reference [Phillips07],where a series of optimized laser-illuminants are designed: they employa blue LD with emission in the range 458-463 nm. Therefore, embodimentsof the invention are non-obvious in that they employ violet LDs, forinstance with a wavelength below 430 nm: this reduces CS, at the expenseof a lower LE. Some embodiments are characterized by a low CS or by alow spectral content (for an SPD normalized to an illuminance of 100 lm)in a CS wavelength range such as 430-520 nm, 440-510 nm or 450-500 nm. Alow spectral content may correspond to less than 10 mW, less than 5 mW,less than 2 mW in said wavelength range.

In various embodiments employing LDs or other narrow-band sources, thewavelength of said sources can be optimized, together with the spectralcharacteristics of the phosphors (peak and width) in order to maximizeproperties of the emitted light while maintaining a desired CS. Theseproperties include the luminous efficacy, and various color renditionmetrics such as CRA Ra, R9, CQS, color gamut metrics, IES color metricsRf and Rg.

FIG. 48A shows a 3-way bulb in an A-lamp form factor. The shown 3-waybulb has two different incandescent filaments (e.g., filament1 4802,filament2 4804), which can be independently controlled for ON/OFF modesof operation.

FIG. 48B shows a 3-way bulb with a screw-in socket. The 3-way bulb takesadvantage of the fact that, for conventional A-lamps with a screw-insocket, there are two points of contact (e.g., line1 4806 and line24808) for the positive signal (e.g., positive 4810). By wiring eachpoint to a different incandescent filament (e.g., filament1 4802,filament2 4804), several operation modes can be enabled. In the offposition, both lines are off. In position A, line 1 carries current andthe corresponding filament lights up. In position B line, 2 carriescurrent and the corresponding filament lights up. In position C, bothlines carry current and both filaments light up. In a typical 3-waybulb, positions A, B and C are respectively identified as low, mediumand high light output.

The 3-way bulb concept has also been adapted to other technologies, suchas fluorescent and LED bulbs. However, the 3-way control is used toprovide different levels of illumination, as in an incandescent 3-wayLED.

The following figures disclose an LED lamp that can output a fewspecific spectra and be controlled by a simple mechanical switch asheretofore described. In one implementation, the lamp is embodied as a3-way A-blub containing two LED sources (e.g., LED1 4842, LED2 4844 asshown in FIG. 48C and FIG. 48D), each with different CCTs. For example:

-   -   cool white (˜5000K)    -   warm white (˜3000K)

The bulb is compatible with a regular 3-way fixture. Depending on theswitch position, the lamp emits light at 3000K, 5000K or about 4000K(e.g., when both LED sources are mixed).

FIG. 48C shows a 3-way bulb with two filament-like LED sources. In thecase of

FIG. 48C, the two LED strings are wired directly to lines 1 and 2. LEDs1 and 2 have different emission spectra such that the visible spectracan emanate from LED1 or from LED2 or from both.

FIG. 48D shows a driver 4819 disposed inside the bulb. Lines 1 and 2both connect to an electrical driver 4819. In this embodiment, thedriver serves several functions:

-   -   It converts the current from AC to a different electrical signal        (for instance DC, or a rectified waveform more amenable to        driving LEDs), and    -   It also performs logic functions such as determining        connectivity and/or routing current and/or varying the magnitude        of the current.

For instance, in a given embodiment, about 10 watts of power areconsumed by the lamp. LED1 has a CCT of 3000K. LED2 has a CCT of 5000K.In position A, only LED1 receives power. In position B, LEDs 1 and 2receive power yielding a CCT between 3000K and 5000K. In position C,only LED2 receives power. In all positions, a similar amount of light isemitted because the same amount of power is driven through the LEDs. Inposition B, the balance of power feeding LEDs 1 and 2 can be tuned toachieve a desired spectrum.

In another embodiment, the total power consumed by the lamp varies withpower. LED1 has a CCT of 2500K, and LED2 has a CCT of 3000K. In positionA, only LED1 receives 4 W of power. In position B, LEDs 1 and 2 receivea total power of 7 W. In position C, only LED2 receives 10 W of power.Thus the CCT of the lamp and its light output vary when the lamp isswitched between positions. The LEDs and combinations may be configuredto reproduce the warm-dimming effect of halogen lamps.

Various other CCT mixes are possible in other embodiments. In some casesthe LEDs may be configured to manage light that has a chromaticities offof the Planckian locus. Some users prefer chromaticities below thePlanckian locus.

FIG. 48E shows such an embodiment. FIG. 48E shows the 1931 (x-y)chromaticity diagram. The Planckian locus is shown, together with thechromaticity of LEDs 1 and 2. LED2, which are both substantiallyon-Planckian with a CCT of 5000K. LED1 is below the Planckian with a CCTof 3000K. Some embodiments are configured such that the mixture of LEDs1 and 2 is off-Planckian with a CCT of about 4000K.

In another embodiment, three LEDs are present rather than two. Each LEDhas a different spectrum. Each position of the 3-way bulb corresponds todriving one or several of the three LEDs.

In some embodiments, the LED sources include violet dies. In someembodiments they include blue dies. In some embodiments the spectraemitted by the distinct LEDs have a different ratio of blue to violet;for instance, one LED has only violet dies and phosphors, and the secondLED has only blue dies and phosphors.

Typically a 3-way bulb has to be used in a compatible fixture with a3-way switch, which will contact either or both of the lines. In someembodiments however, a 3-way switch is integrated to the bulb, ratherthan being in the socket. Therefore the bulb can be placed in aconventional non-3-way fixture. The selection of the emitted spectrumcan be obtained by using the 3-way switch on the bulb.

Aspects of embodiments can be combined, resulting in a light bulb havingtwo or more LED sources, the two or more LED sources having differentspectra, the bulb having at least three electrodes, such that upondriving current in the electrodes the several LED sources can be drivenin at least two configurations to emit two different spectra.

Some phosphors suitable for embodiments have already been discussed inthis application. The following FIG. 49A through FIG. 49C, discuss andexemplify phosphors enabling embodiments. More particularly, some LEDsillumination products have a spectrum (esp. emissions in the blue range)that impacts human circadian cycles and produces unwanted effects in thehuman response system.

Embodiments described herein address the problem of how to suppressunwanted impacts of certain wavelengths of light on humans.Additionally, disclosed herein are several embodiment of lightingapparatus that exhibits a “circadian-friendly” spectrum. The exhibitedminimum in the blue part of the spectrum (e.g., between about 440 andabout 480 nm) reduces impact on human circadian cycles and reduces therelated negative effects. The suppression in the blue part of thespectrum is achieved by using combinations LED chips and LED phosphorsemitting in specific spectral regions. An unexpected result is that thisapproach produces white light balanced on or near the Planckian locusand with general CRI equal to or greater than 80, as well as an R9 valuegreater than 0.

FIG. 49A, FIG. 49B, and FIG. 49C shows the experimental spectra of threeworking examples. The examples describe in detail examples ofconstituent elements of the herein-disclosed embodiments. It will beapparent to those skilled in the art that many modifications, both tomaterials and methods, may be practiced without departing from the scopeof the disclosure.

Strictly as examples, some embodiment have been verified experimentally.Working Example 49A00 is using a blend of BOSE phosphor having anemission peak near 525 nm and SCASN phosphor having an emission peaknear 620 nm, excited by an LED pump with a peak at 414 nm (=see thespectrum in FIG. 49A). The BOSE phosphor is an alkaline earthorthosilicate doped with Eu²⁺ and is typically represented as(Ba,Sr)₂SiO₄:Eu²⁺. The SCASN phosphor is an alkaline earthnitridoaluminosilicate doped with Eu²⁺ and is typically represented as(Sr,Ca)SiAlN₃:Eu²⁺. With CCT=2984K, Duv=+0.0015, 83 CRI and R9=16, 1.24%of this spectrum falls between 440 nm and 480 nm. Working Example 49B00is using a blend of a β-sialon doped with Eu²⁺ phosphor having anemission peak near 530 nm and the same SCASN phosphor and LED pump as inWorking Example 49 (see the spectrum of Working Example 49B00 in FIG.49B). With CCT=3048K, Duv=+0.0003, 80 CRI and R9=27, 0.73% of thisspectrum falls between 440 nm and 480 nm. Working Example 49C00 has thesame phosphors as Working Example 49B00 but is using an LED pump havinga peak at 409 nm (see the spectrum in FIG. 49C). With CCT=3029K,Duv=+0.0001, 84 CRI and R9=13, 1.21% of this spectrum falls between 440nm and 480 nm. In the examples provided here, emission peaks are quotedfor the pure phosphors used.

For the implementation of this invention, it may be important to avoidthe use of SSL pumps emitting with a peak between 435 nm and 480 nm andphosphors emitting with a peak between 400 nm and 500 nm. One possibleemission peak wavelength for the LED pump is in the region between 400nm and 435 nm, more preferably between 405 nm and 425 nm. The SSL pumpmay be an LED chip or SSL laser. The emission peak of phosphors used inthis invention may be above 500 nm, with no primary or secondaryemission peak present between 400 nm and 500 nm. Examples of phosphorsnot meeting the latter criterion are:

-   -   (Ba,Sr,Ca,Mg)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺;    -   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺;    -   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺;    -   Ce_(x)(Mg,Ca,Sr,Ba)_(y)(Sc,Y,La,Gd,Lu)_(1−x−y)Al(Si_(6−z+y)Al_(z−y))(N_(10-z)O_(z))        (where x,y<1, y≥0 and z˜1);    -   (Mg,Ca,Sr,Ba)(Y,Sc,Gd,Tb,La,Lu)₂S₄:Ce³⁺,    -   (which have an emission peak between 400 nm and 500 nm), and    -   (Ba,Sr,Ca,Mg)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺, Mn²⁺;    -   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺, Mn²⁺;    -   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺, Mn²⁺        which have a “secondary” (i.e., of lower intensity) emission        peak between 400 nm and 500 nm from Eu²⁺ emission, even though        their “primary” (i.e., of highest intensity) emission peak is        above 500 nm from Mn²⁺ emission through energy transfer from        Eu²⁺ to Mn²⁺, producing a total of 2 peaks in the emission        spectrum of each of the latter 3 phosphors.

As a general rule, near UV or violet excitable phosphors co-doped by 2activators exhibit a residual blue emission peak from a co-activatoremitting at higher energy (typically Eu²⁺ or Ce³⁺) required to provideenergy to the co-activator emitting at lower energy (typically Mn²⁺),which may render such phosphors unsuitable for some embodiments of thisinvention.

Suitable classes of first phosphors with an emission peak between 500 nmand 550 nm include silicates or fluorosilicates doped with Eu²⁺;chalcogenides doped with Eu²⁺; nitridosilicates, oxynitridosilicates,oxynitridoaluminosilicates or beta-sialons doped with Eu²⁺ andcarbidooxynitridosilicates doped with Eu²⁺. Specific non-limitingexamples of suitable first phosphors include:

-   -   (Ba,Sr)₂SiO₄:Eu²⁺ (a typical formulation of “BOSE”)    -   (Mg,Ca,Sr,Ba,Zn)₂SiO₄:Eu²⁺ (a broader formulation of “BOSE”)    -   (Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺    -   Eux(A1)_(6−z)(A2)_(z)OyN_(8−z)(A3)_(2(x+z−y)), where 0≤z≤4.2;        0≤y≤z; 0<x≤0.1; A1 is Si, C, Ge, and/or Sn; A2 is Al, B, Ga,        and/or In; A3 is F, Cl, Br, and/or I    -   M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2x−x−xy−2w/3)C_(xy)O_(w-v/2)H_(v):A        and    -   M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2x−x−xy−2w/3-v/3)C_(xy)O_(w)H_(v):A,    -   wherein 0<x<1, 0<y<1, 0≤z<1, 0≤v<1, 0<w<1, x+z<1, x>xy+z, and        0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at        least one monovalent cation, M(III) is at least one trivalent        cation, H is at least one monovalent anion, and A is a        luminescence activator doped in the crystal structure.

Suitable classes of second phosphors with an emission peak between 600nm and 670 nm include nitridosilicates doped with Eu²⁺;carbidonitridosilicates doped at least with Eu²⁺; chalcogenides dopedwith Eu²⁺ and oxides, oxyfluorides or complex fluorides doped with Mn⁴⁺.Specific non-limiting examples of suitable second phosphors include:

-   -   (Sr,Ca)AlSiN₃:Eu²⁺ (a typical formulation of “SCASN”)    -   (Ba,Sr,Ca,Mg)AlSiN₃:Eu²⁺ (a broader formulation of “SCASN”)    -   (Ba,Sr,Ca,Mg)_(x)Si_(y)N_(z):Eu²⁺ (where 2x+4y=3z)

The group:

Ca_(1−x)Al_(x−xy)Si_(1−x+xy)N_(2−x−xy)C_(xy) :A   (1);

Ca_(1−x−z)Na_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A   (2);

M(II)_(1−x−z)M(I)_(z)M(III)_(x−xy−z)Si_(1−x+xy+z)N_(2−x−xy)C_(xy):A  (3);

-   -   wherein 0<x<1, 0<y<1, 0≤z≤1, 0≤v<1, 0<w<1, x>xy+z, and        0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at        least one monovalent cation, M(III) is at least one trivalent        cation, H is at least one monovalent anion, and A is a        luminescence activator doped in the crystal structure.    -   (Na,K,Rb,Cs)₂[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   (Mg,Ca,Zr,Ba,Zn)[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   (Mg,Ca,Sr,Ba)(S,Se):Eu²⁺    -   (Na,K,Rb,Cs)₂[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   (Mg,Ca,Zr,Ba,Zn) [(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺    -   Sr[LiAl₃N₄]:Eu²⁺.

In some embodiments, this invention makes use of a first phosphor withan emission peak between 500 nm and 550 nm and a second phosphor with anemission peak between 600 nm and 670 nm. Optionally, one or moreadditional phosphor(s) may be used as needed to optimize the luminousflux or the color rendering properties of the LED. The additionalphosphor(s) may have an emission peak between 500 nm and 670 nm,preferably between 550 nm and 600 nm. Examples of suitable classes ofadditional phosphors include those of the aforementioned first andsecond phosphors classes emitting at different peak wavelengths than thespecific first and second phosphors selected, plus garnets doped withCe³⁺, nitrides doped with Ce³⁺ and alpha-sialons doped with Eu²⁺. Somespecific non-limiting examples of such additional phosphors include:

-   -   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Sc,Al,Ga)₅O₁₂:Ce³⁺    -   (La,Y,Lu)₃Si₆N₁₁:Ce³⁺    -   (Lu,Ca,Li,Mg,Y) alpha-SiAlON doped with Eu²⁺ and/or Ce³⁺.

LED phosphors are typically used as a blend coupled radiationally to theSSL pump, to provide a light spectrum balanced to a certain chromaticity(“color point”) in a given CIE chromaticity diagram, preferably on ornear the Planckian locus, e.g., to within +/−0.010 Duv in the CIE u, vdiagram. The correlated color temperature (CCT) of interest typicallylies between 2200K and 7000K, with CCT values above 2500K preferred forgeneral lighting applications.

Alternatively, the phosphors can be layered sequentially in layers orlaid out in a parallel fashion (e.g., in a pattern of small patches)around the LED pump.

One skilled in the art will know how to adjust the amount of eachphosphor in the phosphor blends, layers or patterns in order to targetany given color point of interest, obtainable per the color mixing ruleas long as it lies within the region subtended by the color points ofeach phosphor and the LED pump in the CIE chromaticity diagram.Achieving LED spectra with good color rendering properties (e.g., asdescribed by the CIE general color rendering index Ra further referredto as “CRI” and the CIE special color rendering index for deep redfurther referred to as “R9”) is however not straightforward since theinfluences of different spectral components are highly non-linear, andthere are no simple rules but rather an element of art involved inobtaining desirable CRI and R9 values, for example. It is traditionallyassumed in the lighting industry that a white spectrum with good colorrendering for general lighting purposes (e.g., with a CRI value of 80 orhigher and an R9 value higher than 0) should have a substantial emissionin the blue wavelength region, especially for CCT values above 2500K.For instance, it has been first predicted by numerical modeling andlater demonstrated experimentally that SPDs with peaks around 450 nm,540 nm and 610 nm provide a CRI of 80 or greater when color-balanced onthe Planckian locus across the range of CCT values used in generallighting. As a consequence, the tri-phosphor fluorescent lamp technologywas developed based on those specific emission peak wavelengths. LEDspectra in the known art have either a pump LED emission peak or aphosphor emission peak in the blue spectral region between 435 nm and500 nm, wherein that phosphor emission peak may be primary or secondary,as explained earlier. Since some white “circadian-friendly” spectrumembodiments need to have emission between 440 nm and 480 nm suppressed,a related impact on the CRI value from this spectral deficiency aroundthe 450 nm wavelength (widely considered critical to CRI based on theaforementioned precedents) can be reasonably expected in comparison totypical white blue-pumped LEDs containing the same green and redphosphors or white violet-pumped LEDs containing a blue-emittingphosphor and the same green and red phosphors. Unexpectedly, someembodiments disclosed here are able to obtain white “circadian-friendly”LEDs exhibiting a local minimum in their spectral power distribution(SPD) between 440 nm and 480 nm and color-balanced near the Planckianlocus with both general CRI80 and R90, as shown in the examples givenhere. This is achieved by using an excess of violet light from the LEDchip (relative to the blackbody spectrum reference) to balance the colornear the Planckian locus, which, contrary to conventional wisdom,affords good CRI (≥80) and R9 (≥0) values without the usage of any peakbetween 435 nm and 500 nm in the spectrum, whether it be from an LEDchip or a phosphor.

The SPD of “circadian-friendly” LEDs prepared according to thisinvention may contain less than 2% of its radiant emission (preferably,less than 1% of its radiant emission) in the spectral region from 440 nmto 480 nm, as demonstrated in the working examples given. When used forgeneral lighting applications, such LEDs can have a general CRI (Ra)value greater than 80 and a special R9 CRI value greater than 0, as alsodemonstrated in the working examples given.

The lighting apparatus disclosed here can be an LED package or module, asolid state lamp (including direct replacement lamps for incandescent,halogen or fluorescent lamps), solid state lighting (“SSL”) fixture,light engine (the light generating component of a fixture), backlightingunit, etc. Whenever the word “LED” is used in the foregoingspecification, it is includes various lighting apparatus, and is notlimiting the scope of applicability of this invention.

In various embodiments related to lighting, the spectrum emitted by theembodiment may be optimized for one or several metrics related toquality of the light. Such metrics may include lumens, luminous efficacyof radiation, chromaticity, CIE Ra, CIE R9 or other special indices, IESRf, IES Rg, other gamut metrics (such as GAI). This optimization can beachieved by selecting the spectral properties of LED emitters andphosphors, as is known in the art. Several examples of such optimizationhave been provided in this disclosure—for instance how the choice of thephosphors enables desirable values of Ra (say >80) or R9 (say >0). Insome embodiments, this optimization is carried out while also optimizingthe spectrum for its circadian properties—for instance by ensuringlittle radiation is present in a given range of circadian stimulation(such as 430-480 nm or others). There is in general a tradeoff betweenthis latter circadian-friendly criterion and other aspects of quality oflight; for instance, a paucity of light in the blue-cyan range may bedetrimental to luminous efficacy of radiation, color rendering (Ra andothers), chromaticity, etc. Therefore, simultaneous optimization for lowcircadian stimulation and other aspects is non-trivial and distinguishesembodiments of the invention from conventional light sources, where onewould naturally include radiation in the blue-cyan range.

In the following, we discuss additional considerations for embodimentsof the invention used in display systems.

In some cases the display is based on an LCD technology and uses colorfilters. Embodiments of the invention use LCDs and filters with hightransmission at short wavelength. For instance, the relativetransmission of the stack composed of the LCD and the blue filter may behigher than 1%, higher than 10%, higher than 20%, or higher than 50% ata wavelength of 415 nm or 420 nm.

FIG. 50A shows an embodiment that uses a white LED based on violetemission with low CS. The LED is combined with three color filters andwith LCDs to produce an RGB screen. Unlike some conventional displays,the short-wavelength transmission of the system (including thetransmission of the blue filter and of the LCD) is maintained atwavelengths in the range of about 410 to about 430 nm.

In some embodiments the system uses more than one primary LED source.This may include a violet and a cyan LED. This is advantageous becauseit increases the gamut of the display. The display may use four filters(violet, cyan, green, red); or it may use only three filters(violet-cyan, green, red) and modulate the violet and cyan LEDs on andoff at the same time as the violet-cyan filter, in order to emulate aviolet pixel and a cyan pixel.

FIG. 50B shows a system with a standard blue-pumped white LED and aviolet LED. Such a system can operate in a circadian stimulating regimeand in a circadian non-stimulating regime. In the stimulating regime,the white LED is on at all times. In the non-stimulating regime, thewhite LED is on and the violet LED is off when the green and red filtersare transmitting; the white LED is off and the violet LED is on when theblue filter is transmitting.

FIG. 50C shows another embodiment where four primaries are used. Here,the switch between non-stimulating and stimulating regime can beobtained by modulating the blue and violet LEDs. Alternately, instimulating mode, both the violet and the blue LED may be usedalternatively in order to enhance the color gamut of the screen.

In some embodiments for display systems, care is taken to use materialsand filters with moderate absorption in the violet range (for instance,in the range of about 410 to about 430 nm). Indeed, violet light may bea necessary aspect to embodiments of the invention as it may replaceunwanted blue and cyan light. In some embodiments of the invention, thetotal transmission of the display system (which may be due to filters,waveguides, diffusers, polarizers and other elements) varies by lessthan 50% (or less than 20%, less than 10%) between 420 nm and 450 nm. Insome embodiments, the total transmission of the display system in therange of about 410 to about 430 nm is more than 20%, more than 50%, morethan 80%.

In some embodiments, the display uses direct emission from LEDs withoutfilters. For instance, each pixel may contain three LEDs (violet, greenand red) or four LEDs (violet, blue/cyan, green and red). An advantageof this configuration is the higher efficiency since no filters arenecessary.

FIG. 50D shows an embodiment with four LEDs in each pixel. Suchembodiments contain no color filters or LCD filters, such thattransmission of short-wavelength light is not reduced.

In some embodiments, the CCT of the display is tuned during theday/night (for instance the CCT becomes warmer at night). This can bescheduled, or linked to an ambient light sensor (photodiode or CCD). Insome cases the ambient CCT is measured and the screen CCT is adapted tomatch the ambient CCT.

In some embodiments with four or more primaries, the emitted spectrumcan be tuned to change the CS. For instance in a system with a violetlight source and a blue/cyan light source, the relative amount of violetand cyan/blue can be tuned from low to high CS.

In some embodiments, the display's brightness can be tuned inrelationship to other quantities like the CCT and the CS. For instance,lower brightness can be associated with a spectrum with lower CS. Againthis can be automated following a schedule (which may take into accountseasons and time of day), and/or a schedule can be learned from theuser's behavior, and/or controlled by the environment (e.g., level oflight, CCT of the ambient light, etc.).

In an embodiment, the system incorporates a digital camera with a CCDsensor; a light level sensor; and a display with a violet and acyan/blue LED whose intensities can be tuned to modify the CS of thescreen's white point. The CCD is used to infer the CCT of ambient light,and the CCT of the screen is adapted accordingly. When the ambient lightlevel is low, the screen brightness is lowered and its CS is low. Whenthe ambient light level is high, the screen brightness is high and itsCS is high.

Additional Embodiments

Any one or more of the herein-discussed techniques can be used to makelight sources (e.g., lamps, display systems, etc.) using the structuresand characteristics of the embodiments below.

-   -   Embodiment 1. A light source comprising:        -   at least one first LED emission source characterized by a            first emission; and        -   at least one second LED emission source characterized by a            second emission; wherein        -   the first emission and the second emission are configured to            provide a first combined emission and a second combined            emission;        -   the first combined emission is characterized by a first SPD            and fractions Fv1 and Fc1;        -   the second combined emission is characterized by a second            SPD and fractions Fv2 and Fc2;        -   Fv1 represents the fraction of power of the first SPD in the            wavelength range from 400 nm to 440 nm;        -   Fc1 represents the fraction of power of the first SPD in the            wavelength range from 440 nm to 500 nm;        -   Fv2 represents the fraction of power of the second SPD in            the wavelength range from 400 nm to 440 nm;        -   Fc2 represents the fraction of power of the second SPD in            the wavelength range from 440 nm to 500 nm;        -   the first SPD and the second SPD have a color rendering            index above 80;        -   Fv1 is at least 0.05;        -   Fc2 is at least 0.1; and        -   Fc1 is less than Fc2 by at least 0.02.    -   Embodiment 2. The light source of embodiment 1, wherein,        -   the first combined emission is characterized by a first            circadian stimulation;        -   the second combined emission is characterized by a second            circadian stimulation; and        -   the second circadian stimulation is at least twice the first            circadian stimulation.    -   Embodiment 3. The light source of embodiment 1, wherein the        first LED emission source comprises at least one LED        characterized by a peak emission in the range 405 nm to 430 nm.    -   Embodiment 4. The light source of embodiment 1, wherein,        -   the first emission and the second emission are configured to            provide a third combined emission;        -   the third combined emission is characterized by a third SPD,            a fraction Fv3, a fraction Fc3, and a third circadian            stimulation;        -   Fv3 represents the fraction of power of the third SPD in the            wavelength range from 400 nm to 440 nm;        -   Fc3 represents the fraction of power of the third SPD in the            wavelength range from 440 nm to 500 nm;        -   the third SPD has a coloring rendering index above 80; and        -   the first circadian stimulation and the third circadian            stimulation are different.    -   Embodiment 5. The light source of embodiment 1, wherein the        second emission comprises blue emission from a wavelength        down-conversion material.    -   Embodiment 6. The light source of embodiment 1, wherein the        second emission comprises direct blue emission from an LED.    -   Embodiment 7. The light source of embodiment 1, wherein one of        the combined emissions induces a circadian stimulation similar        to a circadian stimulation of a D65 reference illuminant.    -   Embodiment 8. The light source of embodiment 1, wherein one of        the combined emissions induces a circadian stimulation that is        less than a circadian stimulation of a CIE A reference        illuminant.    -   Embodiment 9. The light source of embodiment 1, wherein the at        least one first LED emission source and the at least one second        LED emission source are configured in an intermixed physical        arrangement.    -   Embodiment 10. The light source of embodiment 1, wherein each of        the first SPD and the second SPD is characterized by a        chromaticity within the white light bounding region 514 of FIG.        5B.    -   Embodiment 11. The light source of embodiment 10, wherein each        of the first SPD and the second SPD is characterized by a        chromaticity bounded by ±0.005 of a Planckian loci and by ±0.005        of a minimum-hue-shift curve in a CIE chromaticity diagram.    -   Embodiment 12. The light source of embodiment 1, wherein each of        the first SPD and the second SPD is characterized by a        chromaticity within +/−five Du′v′ points of a Planckian loci.    -   Embodiment 13. The light source of embodiment 1, wherein        exposure of a subject to the second SPD with an illuminance of        100 lx for ninety minutes results in a suppression of blood        melatonin concentration in the subject of at least 20%.    -   Embodiment 14. The light source of embodiment 1, wherein        exposure of a subject to the first SPD with an illuminance of        100 lx for ninety minutes results in a suppression blood        melatonin concentration in the subject of at most 20%.    -   Embodiment 15. The light source of embodiment 1, wherein Fc1 is        at most 0.06.    -   Embodiment 16. A display system comprising:        -   a first LED emission source characterized by a first            emission; and        -   a display configured to emit a first SPD characterized by a            first fraction Fv1 of power in the range 400 nm to 435 nm;            wherein,        -   the display system is characterized by a color gamut of at            least 70% of NTSC;        -   the first SPD is substantially white with a CCT in a range            from 3000K to 9000K; and        -   Fv1 is at least 0.05.    -   Embodiment 17. The display system of embodiment 16, wherein the        display comprises an emission spectrum characterized by a        circadian stimulation that is less than a circadian stimulation        of a reference illuminant having the same CCT.    -   Embodiment 18. The display system of embodiment 16, further        comprising a color filter set and a liquid crystal display.    -   Embodiment 19. The display system of embodiment 18, wherein,        -   the first SPD is characterized by a peak in the wavelength            range from 400 nm to 435 nm at a wavelength w;        -   the color filter set comprises a blue filter characterized            by a maximum transmission Tm, and by a transmission Tw at            wavelength w; and        -   Tw/Tm>0.8.    -   Embodiment 20. The display system of embodiment 16, further        comprising a second LED emission source characterized by a        second emission, wherein a ratio of the first emission and the        second emission are configured to be adjusted to change a        circadian stimulation.    -   Embodiment 21. The display system of embodiment 16, wherein the        display system is configured for use with a TV, desktop PC,        notebook PC, laptop PC, tablet, smartphone, MP3 player.    -   Embodiment 22. The display system of embodiment 16, wherein less        than 5% of the total power of the first SPD is in a wavelength        range from 440 nm to 500 nm.

FIG. 51A and FIG. 51B illustrate reducing loss by generating a spectrumthat already has only a small portion of radiation in the CSR, in caseswherein radiation within the CSR is desired to be completely ornear-completely removed by absorption and/or filtering. The two originalspectral power distributions are both observed by human viewers ashaving substantially the same chromaticity. In the case of FIG. 51A andFIG. 51B specifically, they are both white emitters (near the blackbodyloci) and further demonstrate reasonably high color rendering (CRI of80). This is possible since human visual sensation of blue light can bestimulated by blue light or a violet light. In many cases a relativelylarger amount of power in violet ranges (FIG. 51B) produces the samehuman sensation as a relatively smaller amount of power in bluewavelength ranges (FIG. 51A).

However, filtering of emitted blue light (e.g., so as to completely ornear-completely remove radiation in the CSR) as shown in FIG. 51A hasthe side effect of significantly reducing power efficiency of thecorresponding lamp, as well as significantly changing its chromaticity(i.e., making the emission appear strongly yellow). In contrast, thespectral power distribution as shown in FIG. 51B does not produce asubstantial amount of radiation in the CSR in the first place, and sodoes not suffer significantly reduced useful radiation when residualemission in the CSR is removed. Furthermore, its chromaticity is onlyslightly affected by removing light in the CSR and can be easilycompensated for (to retain a white color point) through slightmodifications to the phosphor and/or primary violet LED emissions.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the claims are not to be limited to the details given herein, butmay be modified within the scope and equivalents thereof.

1-23. (canceled)
 24. A method of using a lighting system to emit emittedlight having a relatively high illuminance but a relatively lowcircadian stimulation, said light system having at least one solid-statelighting emitter, and at least a first and second additional lightemitters for cooperating with said lighting emitter such that saidemitted light is white light, said method comprising: applying power tosaid lighting system thereby causing at least said light emitter andsaid first and second additional light emitters to emit said emittedlight having a certain correlated color temperature (CCT), the lightingsystem being configured to produce an illuminance of about 50 lux toabout 5000 lux, and a circadian stimulation no greater than about 50% ofa reference circadian stimulation of a reference illuminant configuredto produce an illuminance essentially the same as said predeterminedilluminance and a CCT the same as said certain CCT.
 25. The method ofclaim 24, wherein said circadian stimulation is no greater than about20% of said reference circadian stimulation.
 26. The method of claim 24,wherein the light emitter comprises at least one light-emitting diode orone laser diode emitting having a peak wavelength in a range 400-430 nm,said first additional light emitter has an emission spectrum having apeak between 500 nm and 550 nm, and said second additional light emitterhas an emission spectrum having a peak between 600 nm and 670 nm. 27.The method of claim 24, wherein said lighting system comprises no lightemitting species having a peak emission at a wavelength in a range440-490 nm.
 28. The method of claim 24, wherein the emitted light ischaracterized by a spectral power distribution (SPD), wherein the SPDhas a local minimum in a spectral region between 440 nm and 480 nm and apower in the SPD between 440 nm and 480 nm is less than 2% of a power ofthe SPD between 380 nm and 780 nm.
 29. The method of claim 24, whereinsaid emitted light has a CRI Ra higher than 80 and a CRI R9 higher than0.
 30. The method of claim 24, wherein said emitted light has a CRI R9higher than
 80. 31. The method of claim 24, wherein said certain CCT isat least 2700K and a distance from the Planckian locus Duv which issmaller than +/−0.006.
 32. The method of claim 24, wherein theilluminance is a retinal illuminance.
 33. The method of claim 24,further comprising selecting a circadian action spectrum, and whereinsaid circadian stimulation is calculated as an integral of said SPDweighed by said circadian action spectrum.
 34. The method of claim 24,wherein said first and second additional light emitters are phosphorlight-converting materials.
 35. The method of claim 24, wherein saidreference illuminant is a CIE CRI reference illuminant.